Rotating electrical machine

ABSTRACT

A rotating electrical machine includes a rotor and a magnet unit. The rotating electrical machine also includes a cylindrical stator and a housing. The stator is equipped with a stator winding made up of a plurality of phase windings. The stator is arranged coaxially with the rotor and faces the rotor. The housing has the rotor and the stator disposed therein. The rotor includes a cylindrical magnet retainer to which the magnet unit is secured and an intermediate portion which connects between a rotating shaft of the rotor and the magnet retainer and extends in a radial direction of the rotating shaft. A first region located radially inside an inner peripheral surface of a magnetic circuit component made up of the stator and the rotor is greater in volume than a second region between the inner peripheral surface of the magnetic circuit component and the housing in the radial direction.

CROSS REFERENCE TO RELATED DOCUMENTS

This Application is a Divisional of application Ser. No. 16/748,195filed Jan. 21, 2020, which claims the benefit of priority of JapanesePatent Application Nos. 2017-142223 filed on Jul. 21, 2017, 2017-142224filed on Jul. 21, 2017, 2017-142225 filed on Jul. 21, 2017, 2017-142226filed on Jul. 21, 2017, 2017-142227 filed on Jul. 21, 2017, 2017-142228filed on Jul. 21, 2017, 2017-255048 filed on Dec. 28, 2017, 2017-255049filed on Dec. 28, 2017, 2017-255050 filed on Dec. 28, 2017, 2017-255051filed on Dec. 28, 2017, 2017-255052 filed on Dec. 28, 2017, and2017-255053 filed on Dec. 28, 2017, disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a rotating electrical machine.

BACKGROUND ART

A device which is capable of having a rotating machine and an inverterdevice built therein have been proposed as a rotating electrical machine(e.g., Patent Literature 1). In patent literature 1, a stator and arotor of the rotating machine are of a circular ring-shape. The inverterdevice is disposed in space inside the stator and the rotor.

PRIOR ART DOCUMENT

-   Patent literature 1 Japanese patent first publication No.    2004-213622-   Patent literature 2 Japanese patent first publication No.    2004-213622-   Patent literature 3 Japanese patent first publication No. 2011-78298-   Patent literature 4 Japanese patent first publication No.    2012-165614-   Patent literature 5 Japanese patent first publication No. 1996-70522-   Patent literature 6 Japanese patent first publication No.    2012-175755

SUMMARY OF THE INVENTION

In a case there the rotating electrical machine, as taught in the abovepatent literature 1, has a heat generating member, such as an inverterdevice, disposed inside the stator and the rotor, it is necessary toeffectively dissipate heat. Particularly, a coil used with the stator orthe rotor generates heat. It is, therefore, necessary to ensure a heatdissipating ability.

The present invention was made in view of the above problem. It is aprincipal object of the invention to provide a rotating electricalmachine which has a suitable storage space and suitable ability todissipate heat.

The first disclosure relates to a rotating electrical machine whichcomprises: (a) a rotor which includes a rotor body with a hollow portionand a magnet unit mounted on the rotor body, the rotor being retained tobe rotatable; (b) a cylindrical stator which is equipped with a statorwinding including a plurality of phase-windings, the stator beingarranged to face the rotor coaxially therewith; and (c) a housing inwhich said rotor and said stator are disposed. The rotor body includes acylindrical magnet retainer to which the magnet unit is secured and anintermediate portion that is a portion connecting a rotating shaft ofthe rotor and the magnet retainer and extends in a radial direction ofthe rotating shaft. A first region, as defined radially inside an innerperipheral surface of a magnetic circuit component made of the statorand the rotor, is greater in volume than a second region, as definedbetween the inner peripheral surface of the magnetic circuit componentand the housing in the radial direction.

With the above arrangements, the first region is defined on a side ofthe inner peripheral surface of the magnetic circuit component, but hasa volume greater than that of the second region defined between theinner peripheral surface of the magnetic circuit component and thehousing. This facilitates dissipation of more heat from first regionthan from the second region, thereby achieving suitable heat dissipationability.

In the second disclosure, if a radius of an inner periphery of thehousing is defined as d in the first disclosure, the magnetic circuitcomponent is located radially outside a distance of d×0.705 away fromthe center of rotation.

With the above arrangements, the first region defined radially insidethe inner peripheral surface of the magnetic circuit component withinthe housing has a volume greater than that of the second region definedbetween the inner peripheral surface of the magnetic circuit componentand the housing in the radial direction, thereby offering suitableability to dissipate the heat.

The third disclosure relates to a rotating electrical machine whichcomprises: (a) a rotor which includes a rotor body with a hollow portionand a magnet unit mounted on the rotor body, the rotor being retained tobe rotatable; (b) a cylindrical stator which is equipped with a statorwinding including a plurality of phase-windings, the stator beingarranged to face the rotor coaxially therewith; and (c) a housing inwhich said rotor and said stator are disposed. The rotor body includes acylindrical magnet retainer to which the magnet unit is secured and anintermediate portion that is a portion connecting a rotating shaft ofthe rotor and the magnet retainer and extends in a radial direction ofthe rotating shaft. If a radius of an inner periphery of the housing isdefined as d, a magnetic circuit component made up of the stator and therotor is located radially outside a distance of d×0.705 away from thecenter of rotation.

With the above arrangements, a region defined radially inside an innerperipheral surface of the magnetic circuit component within the housinghas a volume greater than that of a region defined between the innerperipheral surface of the magnetic circuit component and the housing inthe radial direction, thereby offering suitable ability to dissipateheat.

The fourth disclosure relates to the structure, as set forth in any oneof the first to third disclosures, wherein the intermediate portion islocated away from a center of the rotor in an axial direction of therotor.

With the above arrangements, the volume of the first region definedradially inside the inner peripheral surface of the magnetic circuitcomponent is increased as compared with when the rotor has theintermediate portion in the center thereof or on both axial endsthereof. The intermediate portion is located away from the center of therotor in one of opposite axial directions. The rotor, therefore, has anopening facing away from the intermediate portion and facilitatesdissipation of heat therefrom, thereby improving the suitable ability todissipate the heat.

The fifth disclosure relates to the structure, as set forth in any oneof the first to fourth disclosure, wherein the rotor is of an outerrotor structure in which the rotor is arranged radially outside therotor. The magnet unit is secured to a radially inner side of the rotorbody.

The above arrangements, unlike the inner rotor structure, enable themagnet unit to be retained radially inside the rotor body withoutaccidentally detaching when the magnet unit is subjected to centrifugalforce during rotation of the rotor. In other words, a structure requiredto secure magnets to the rotor body may be minimized as compared withthe inner rotor structure. For instance, a surface magnet type rotor maybe employed. This enables the rotor to have a decreased thickness ascompared with the inner rotor structure, thereby increasing the size ofthe first region defined radially inside the inner peripheral surface ofthe magnetic circuit component.

The sixth disclosure relates to the structure, as set forth in the fifthdisclosure, wherein the rotating electrical machine also includes astator retainer which retains the stator. The stator retainer includes acylinder attached to a radial inner side of the stator, and wherein thecylinder is equipped with a cooling portion.

The cooling portion works to release heat from the magnetic circuitcomponent and also cool a member disposed in the first region definedradially inside the magnetic circuit component within the cylinder. Thecooling portion having ability to suitably cool the magnetic circuitcomponent enables the first region to dissipate heat therefrom becauseit has a size greater than that of the second region defined between theinner peripheral surface of the magnetic circuit component and thehousing even when a heat generating member which generates an amount ofheat equal to or less than that produced by the magnetic circuitcomponent is disposed in the first region.

The seventh disclosure relates to the structure, as set forth in thesixth disclosure, wherein an electrical component is disposed inside thecylinder. The electrical component includes heat generating memberswhich generates heat when electrically energized. The heat generatingmembers are arranged along an inner peripheral surface of the cylinder.The cooling portion are arranged to overlap the heat generating membersin a radial direction.

With the above arrangements, the cooling portion works to dissipate heatfrom the magnetic circuit component and also cool the electricalcomponent effectively.

The eighth disclosure relates to the structure, as set forth in any oneof the first to seventh disclosures, wherein an electromagneticwave-generating member is disposed in a region which is located radiallyinside an inner peripheral surface of the magnetic circuit component.

The magnetic circuit component made up of the housing, the rotor and thestator is disposed radially outside the first region defined radiallyinside the inner peripheral surface of the magnetic circuit component,thereby minimizing dissipation of electromagnetic noise generated by theelectromagnetic wave-generating member to the outside.

The ninth disclosure relates to the structure, as set forth in any oneof the first to eighth disclosure, wherein the magnet unit has differentmagnetic poles arranged on a surface of the rotor which faces thestator. The different magnetic poles are alternately arrayed in acircumferential direction of the rotor. The stator haswinding-to-winding members each of which is arranged betweencircumferentially adjacent magnet facing portions. If a width of thewinding-to-winding members energized by excitation of the stator windingin a circumferential direction within a portion of the magnet unitequivalent to one of magnetic poles is defined as Wt, a saturationmagnetic flux density of the winding-to-winding members is defined asBs, a width of the magnet unit equivalent to one of the magnetic polesof the magnet unit in a circumferential direction of the magnet unit isdefined as Wm, and a remanent flux density in the magnet unit is definedas Br, the winding-to-winding members are made of a magnetic materialmeeting a relation of Wt×Bs≤Wm×Br or a non-magnetic material.

The above structure enables a conductor sectional area of the statorwinding to be increased, thereby minimizing the amount of heat generatedtherefrom. It is also possible to have a thickness of the stator windingwhich is increased in the radial direction to increase the volume of thefirst region defined radially inside the inner peripheral surface of themagnetic circuit component.

The tenth disclosure relates to the structure, as set forth in the ninthdisclosure, wherein the stator winding includes anisotropy conductors.

In the case of the slot-less structure, the conductors of the statorwinding has an increased density. The use of the anisotropy conductorsfacilitates the design of electrical insulation.

The eleventh disclosure relates to the structure, as set forth in anyone of the first to tenth disclosure, wherein if an outer diameter of anair gap between the rotor and the stator is defined as D, and the numberof poles is defined as P, a relation of D/P<12.2 is met.

The above structure enables the first region defined radially inside theinner peripheral surface of the magnetic circuit component to have avolume greater than that of the second region defined between the innerperipheral surface of the magnetic circuit component and the housingwithout sacrificing the torque to be outputted.

The twelfth disclosure relates to the structure, as set forth in any oneof the first to eleventh disclosure, wherein the rotor is made of asurface magnet type rotor in which permanent magnets are secured to therotor body as the magnet unit. The magnet unit includes first magnetswhose magnetization direction is oriented in a radial direction of therotating shaft and second magnets whose magnetization direction isoriented in a circumferential direction of the rotating shaft. Themagnet unit is designed in a magnet array in which the first magnets arearranged at a given interval away from each other in the circumferentialdirection. Each of the second magnets is disposed in thecircumferentially adjacent first magnets.

The use of the surface magnet type rotor enables a used amount ofmagnetic metal material, such as iron, to be minimized to decrease thethickness of the rotor. The use of the above magnetic array reducesleakage of magnetic flux from the permanent magnets to create a magneticcircuit in the rotor. In other words, it is possible to fully achievethe function of the rotor 40 to create the magnetic circuit only by thepermanent magnets. This structure enables the thickness to be decreased,thereby improving the output torque and increasing the volume of thefirst region defined radially inside the inner peripheral surface of themagnetic circuit component.

The thirteenth disclosure relates to the structure, as set forth in anyone of the first to eleventh disclosure, wherein the rotor is made of asurface magnet type rotor in which permanent magnets are secured to therotor body as the magnet unit. The magnet unit is made of polaranisotropic magnets.

The use of the surface magnet type rotor enables a used amount ofmagnetic metal material, such as iron, to be minimized to decrease thethickness of the rotor. The use of the above magnetic array reducesleakage of magnetic flux from the permanent magnets to create a magneticcircuit in the rotor. In other words, it is possible to fully achievethe function of the rotor to create the magnetic circuit only by thepermanent magnets. This structure enables the thickness to be decreased,thereby improving the output torque and increasing the volume of thefirst region defined radially inside the inner peripheral surface of themagnetic circuit component.

The fourteenth disclosure relates to the structure, as set forth in anyone of the first to thirteenth disclosure, which also includes bearingswhich are disposed in the housing and retain the rotating shaft of therotor to be rotatable. The rotating shaft is rotatably held by thebearings arranged at locations different from each other in the axialdirection of the rotating shaft. The bearings are disposed away from acenter of the rotor in the axial direction.

In a cantilever structure in which the bearings are arranged close toone of the axially opposed sides, heat generated by the bearings usuallyconcentrates only on one of the axially opposed sides. This enhances thedissipation of heat from a place located farther away from the bearingsin a case where a heat generating member, such as a capacitor, isdisposed in the first region defined radially inside the innerperipheral surface of the magnetic circuit component.

The fifteenth disclosure relates to a rotating electrical machine whichcomprises: (a) a rotor which includes a cylindrical rotor body with ahollow portion and a magnet unit mounted on the rotor body, the rotorbeing retained to be rotatable; (b) a cylindrical stator which isequipped with a stator winding including a plurality of phase-windings,the stator being arranged to face the rotor coaxially therewith; (c) ahousing in which said rotor and said stator are disposed; (d) a statorwhich includes a stator winding made up of a plurality of phasewindings, the stator being arranged coaxially with the rotor and facingthe rotor; (e) a housing which secures the stator; and (f) bearingswhich are disposed in the housing and retain the rotating shaft of therotor to be rotatable. The rotating shaft is rotatably held by thebearings arranged at locations different from each other in the axialdirection of the rotating shaft. The bearings are disposed away from acenter of the rotor in the axial direction.

Conventional rotating electrical machines capable of having an inverterdevice built together with a rotating machine have been proposed (e.g.,patent literature 2). In patent literature 2, a stator and a rotor ofthe rotating machine are of a circular shape. The inverter device isdisposed in space formed inside the stator and the rotor.

The rotating electrical machine taught in patent literature 2 isretained by a shift of a vehicle using a pair of bearings to berotatable. Specifically, the shaft has mounted thereon a pair of wheeldiscs located away from each other in an axial direction of the shaft.The rotating electrical machine is rotatable relative to the shaft usingthe bearings mounted on central portions of the wheel discs. Theinverter device is arranged between the wheel discs in the axialdirection.

Therefore, in the rotating electrical machine disclosed in patentliterature 2, the inverter device equipped with a heat generatingmember, such as a capacitor, is disposed in space surrounded by thebearings which usually generate heat during rotation thereof, so thatthe heat hardly dissipate from the space.

It is, therefore, principal object of the fifteenth disclosure toprovide a rotating electrical machine which has suitable ability todissipate heat. In the fifteenth disclosure, the cantilever structure inwhich the bearings are located only on one of axially opposed sides isused, so that heat generated by the bearings concentrates only on one ofthe axially opposed sides. This causes heat to be released effectivelyfrom a place facing away from the bearings even when a heat generatingmember, such as a capacitor, is arranged in the hollow portion of therotor body.

The sixteenth disclosure relates to the structure, as set forth in thefifteenth disclosure, wherein the bearings are radial ball bearingsequipped with an outer race, an inner race, and balls disposed betweenthe outer race and the inner race. One of the bearings is designed to bedifferent in dimension of a gap between each of the outer race and theinner race and the balls from the other of the bearings.

The above structure effectively absorbs swinging or vibration of thebearings due to imbalance resulting from oscillation of the rotor orparts tolerance at a location close to the center of the rotor.

The seventeenth disclosure relates to the structure, as set forth in thefifteenth or sixteenth disclosure, wherein the rotor is made of asurface magnet type rotor in which permanent magnets are secured to therotor body.

In the case of use of the cantilever arrangement, the weight of aportion of the rotor which is far away from the bearings will beincreased, so that the inertia is increased, thereby resulting in anincrease in swinging or vibration of the rotor. The rotor is, therefore,designed in the form of the surface magnet type. This enables a usedamount of magnetic metal material to be decreased as compared with anIPM rotor, thereby resulting in a decrease in inertia. It is, therefore,possible to reduce the swinging or vibration of the rotor even with theuse of the cantilever arrangement.

The eighteenth disclosure relates to the structure, as set forth in theseventeenth disclosure, wherein the permanent magnets include firstmagnets whose magnetization direction is oriented in a radial directionof the rotating shaft and second magnets whose magnetization directionis oriented in a circumferential direction of the rotating shaft. Themagnet unit is designed in a magnet array in which the first magnets arearranged at a given interval away from each other in the circumferentialdirection. Each of the second magnets is disposed in thecircumferentially adjacent first magnets.

The use of the above magnetic array reduces leakage of magnetic fluxfrom the permanent magnets to create a magnetic circuit in the rotor. Inother words, it is possible to fully achieve the function of the rotorto create the magnetic circuit only by the permanent magnets. Thisstructure enables the rotor body which retains the permanent magnetsexhibiting inertia to be made of synthetic resin, such as CFRP, notmagnetic metallic material, thereby minimizing the inertia. It is,therefore, possible to use the cantilever structure to minimize theinertia to reduce the swinging or vibration of the rotor.

The nineteenth disclosure relates to the structure, as set forth in theseventeenth disclosure, wherein the permanent magnets are made of polaranisotropic magnets.

It is possible to reduce adverse effects of demagnetization, as comparedwith a magnet array called a Halbach array.

The twentieth disclosure relates to the structure, as set forth in anyone of the fifteenth to nineteenth disclosure, wherein the rotor is ofan outer rotor structure in which the rotor is arranged radially outsidethe stator.

The above structure has the magnet unit secured radially inside therotor body, thereby firmly holding the magnet unit radially inside therotor body using the rotor body, unlike the inner rotor structure, whencentrifugal force acts on the magnet unit during rotation of the rotor.In other words, as compared to the inner rotor structure, a structurerequired to secure the magnets to the rotor body enables to beminimized. This minimizes the inertia to reduce the swinging orvibration of the rotor even with the use of the cantilever structure.

The twenty-first disclosure relates to the structure, as set forth inany one of the fifteenth to twentieth disclosure, wherein the rotor bodyincludes a cylindrical magnet retainer to which the magnet unit issecured, an fixing portion which is of a cylindrical shape and smallerin diameter than the magnet retainer and through which the rotatingshaft passes, and an intermediate portion connecting between the magnetretainer and the fixing portion. The fixing portion to which therotating shaft is secured to be rotatable along with the fixing portionis attached to the housing through the bearings to be rotatable. Theintermediate portion includes a radially inner portion and a radiallyouter portion and has a difference in level between the radially innerportion and the radially outer portion in the axial direction. Themagnet retainer and the fixing portion partially overlap each other inthe axial direction.

The above structure results in a decrease in axial length of therotating electrical machine and ensures required lengths of the magnetretainer and the fixing portion in the axial direction. The ensuring ofthe required length of the fixing portion enables the bearings to have arequired interval therebetween, thereby achieving the stability inoperation of the bearings. It is possible to partially place thebearings close the center of gravity of the rotor, thereby furtherenhancing the stability in operation of the bearings.

The twenty-second disclosure relates to the structure, as set forth inany one of the fifteenth to twenty-first disclosure, wherein the rotoris equipped with an air cooling fin.

The air cooling fan works to effectively release heat.

The twenty-third disclosure relates to the structure, as set forth inany one of the fifteenth to twenty-second disclosure, wherein the rotorbody has an opening located farther away from the bearings in the axialdirection.

The above structure enables the heat to be dissipated effectively fromthe opening even when a heat generating member is mounted inside therotor. Since there is no bearing which will generate heat duringrotation thereof near the opening, a flow of air is created into theopening, thereby enhancing the dissipation of heat.

The twenty-fourth disclosure relates to a rotating electrical machinewhich comprises: (a) a rotor which is equipped with a magnet unit whichgenerates magnetic flux and retained to be rotatable; and (b) a statorwhich is equipped with a stator winding made up of a plurality of phasewindings, the stator being arranged coaxially with the rotor and facingthe rotor. The magnet unit includes first magnets whose magnetizationdirection is oriented in a radial direction of the rotor and secondmagnets whose magnetization direction is oriented in a circumferentialdirection of the rotor. The first magnets are arranged at a giveninterval away from each other in the circumferential direction. Each ofthe second magnets is disposed in the circumferentially adjacent firstmagnets. The magnet unit has end surfaces of the first magnets whichface away from the stator and end surfaces of the second magnets whichface away from the rotor. At least the end surfaces of the first magnetsor the end surfaces of the second magnets define recesses hollowedtoward the stator in the radial direction. The magnetic members aredisposed in the recesses in a surface of the rotor which faces away fromthe stator.

Rotating electrical machines in which permanent magnets are disposed ina given array to increase the magnetic flux density are known (e.g.,patent literature 3). The rotating electrical machine in patentliterature 3 has the permanent magnets which include first magnets whosemagnetization direction is oriented in a radial direction and secondmagnets whose magnetization direction is oriented in a circumferentialdirection. The first magnets are arranged in the circumferentialdirection. Each of the second magnets is disposed between thecircumferentially adjacent first magnets radially outside the firstmagnets. Each of the first magnets has the magnetization directionoriented in a direction opposite that of the adjacent first magnet.Similarly, each of the second magnets has the magnetization directionoriented in a direction opposite that of the adjacent second magnet. Acore segment is disposed radially outside the first magnets between arespective two of the second magnets. This increases the density ofmagnetic flux toward the stator and enables the rotating electricalmachine to output a high degree of torque.

The rotating electrical machine taught in patent literature 3 has thefirst magnets secured to a shaft, thus leading to a risk that magneticsaturation may occur in a magnetic path in the shaft. The magneticsaturation results in a decrease in a flow of magnetic flux, therebycausing demagnetization of the first magnets. The decrease in magneticflux density will result in a lowered output from the rotatingelectrical machine.

It is, therefore, a principal object of the twenty-fourth disclosure toprovide a rotating electrical machine which is designed to facilitateflow of the magnetic flux. The magnet unit in the twenty-fourthdisclosure has the recesses in the end surfaces of the first magnetsfacing away from the stator and/or the end surfaces of the secondmagnets facing away from the stator. The recesses are hollowed towardthe stator in the radial direction. The rotor has the soft magneticmaterial-made members disposed in the recesses in order to facilitateflow of magnetic flux from the magnets, thereby improving the density ofmagnetic flux flowing toward the stator.

For instance, in a case where the magnet retainer made from softmagnetic material is disposed over the first and second magnets arrangedcircumferentially adjacent each other in the above magnet layout on anopposite side of the magnet unit to the stator, there is a risk that amagnetic path in the magnet retainer may be magnetically saturated.Particularly, there is a high probability that the magnetic saturationoccurs at a boundary between the first and second magnets. Theoccurrence of magnetic saturation in the magnet retainer will causemagnetic flux to bypass a place where the magnetic saturation occurs,thereby resulting in distortion of the magnetic path which causes thedemagnetization.

In order to alleviate the above problem, the recesses are formed in thesurface of the magnet unit facing away from the stator. The magneticmembers made from soft magnetic material are disposed in the recesses,thereby alleviating the risk of magnetic saturation to avoid thedemagnetization of the magnets. This avoids a reduction in output fromthe rotating electrical machine.

For instance, even when there is no magnet retainer made from softmagnetic material on the opposite side of the magnet unit to the stator,the magnetic members serve to reduce leakage of magnetic flux from theopposite side of the magnet unit to the stator, thereby improving thedensity of magnetic flux flowing toward the stator.

The twenty-fifth disclosure relates to the structure, as set forth inthe twenty-fourth disclosure, wherein a thickness of either of the firstmagnets or the second magnets in the radial direction is set smallerthan that of the other of the first magnets and the second magnets todefine the recesses, and wherein the magnetic members are arranged awayfrom the stator in the first magnets or the second magnets, whicheverare smaller in thickness.

The above structure facilitates flow of magnetic flux from the magnets,thereby improving the density of magnetic flux flowing toward thestator.

The twenty-sixth disclosure relates to the structure, as set forth inthe twenty-fourth disclosure, wherein the first magnets have a thicknessin the radial direction which is selected to be smaller than that of thesecond magnets to define the recesses. The magnetic members are disposedin portions of the first magnets which are located away from the stator.The sum of the thickness of each of the first magnets and a thickness ofa corresponding one of the magnetic members in the radial direction isequal to the thickness of each of the second magnets in the radialdirection.

The first magnets whose magnetization direction is oriented in theradial direction have portions which are located farther away from thestator and most magnetized. The demagnetization may, therefore, be byminimized by placing the magnetic members inside or outside the firstmagnets in the radial direction. This also enables the volume of thefirst magnets to be decreased. The sum of the thickness of each of thefirst magnets and the thickness of a corresponding one of the magneticmembers in the radial direction is selected to be equal to the thicknessof each of the second magnets in the radial direction, therebyfacilitating flow of magnetic flux to improve the density of themagnetic flux.

The twenty-seventh disclosure relates to the structure, as set forth inthe twenty-fourth disclosure, wherein ones of the first magnets havemagnetization directions oriented toward the stator. The magneticmembers are disposed in the ones of the first magnets away from thestator.

The above structure effectively avoids a reduction in copper loss in therotor and minimizes the demagnetization.

The twenty-eighth disclosure relates to the structure, as set forth inthe twenty-fourth disclosure, wherein the second magnets have athickness in the radial direction which is selected to be smaller thanthat of the first magnets to define the recesses. The magnetic membersare disposed in portions of the second magnets which are located awayfrom the stator. The sum of the thickness of each of the second magnetsand a thickness of a corresponding one of the magnetic members in theradial direction is equal to the thickness of each of the first magnetsin the radial direction.

The demagnetization may, therefore, be by minimized by placing themagnetic members inside or outside the second magnets in the radialdirection. This also enables the volume of the second magnets to bedecreased. The sum of the thickness of each of the second magnets andthe thickness of a corresponding one of the magnetic members in theradial direction is selected to be equal to the thickness of each of thefirst magnets in the radial direction, thereby facilitating flow ofmagnetic flux to improve the density of the magnetic flux.

The twenty-ninth disclosure relates to the structure, as set forth inany one of the twenty-fourth to twenty-eighth disclosures, wherein therotor is equipped with a magnet retainer which is made from softmagnetic material and retains the magnetic members together with themagnet unit. The magnet retainer is disposed on a portion of the magnetunit which faces away from the stator. The magnet retainer extends overthe first magnets and the second magnets which are disposed adjacenteach other in the circumferential direction.

The use of the magnet retainer which is made from soft magnetic materialand disposed on a portion of the magnet unit which faces away from thestator, thereby avoiding leakage of magnetic flux from the portion ofthe magnet unit facing away from the stator to improve the magnetic fluxdensity toward the stator. The magnet retainer has a risk that themagnetic path becomes magnetically saturated and demagnetizes the firstmagnets. The recesses, as described above, alleviate the magneticsaturation to minimize the demagnetization of the magnets.

The thirtieth disclosure, as set forth in any one of the twenty-fourthto twenty-ninth disclosures, wherein the second magnets have a length inthe circumferential direction which lies in a range of 52<α<80 where αis an electrical angle [degE].

The mounting of the magnetic members usually causes an optimum value ofan angle between commutating poles that is typically 60 [degE] to beshifted to 68 [degE]. This enables the second magnets (i.e., thecommutating poles) to be designed to lie in the above range to achievethe mechanical rotation stop without demagnetization.

The thirty-first disclosure relates to the structure, as set forth inany one of the twenty-fourth to thirtieth disclosures, wherein the rotoris of an outer rotor structure in which the rotor is arranged radiallyoutside the stator.

The outer rotor structure has a lower probability that the magnets areaccidentally dislodged by centrifugal force than the inner rotorstructure. This eliminates the need for dislodging avoiding members andenables the rotor to have a decreased thickness and the size of the airgap between the stator and the rotor to be decreased, thereby improvingthe torque output.

The thirty-second disclosure relates to the structure, as set forth inany one of the twenty-fourth to thirty-first disclosure, wherein therotor is equipped with a magnet retainer which retains said magneticmembers together with the magnet unit. The magnetic members are equippedwith engaging portions which are arranged in the circumferentialdirection and engage the magnet retainer.

Usually, the stop of rotation relative to the magnet retainer may bewell achieved by designing the magnetic members which are higher inmechanical properties (i.e., rigidity) than the magnets to have engagingportions.

The thirty-third disclosure relates to the structure, as set forth inany one of the twenty-fourth to thirty-second disclosure, wherein thefirst magnets include a first A magnet whose magnetization direction isoriented outwardly in the radial direction and a first B magnet whosemagnetization direction is oriented inwardly in the radial direction.The second magnets include a second A magnet whose magnetizationdirection is oriented in a first one of opposite circumferentialdirection and a second B magnet whose magnetization direction isoriented in a second one of the opposite circumferential direction. Themagnet unit is designed to have the first A magnet, the second A magnet,the first B magnet, and the second B magnet arranged in this order inthe circumferential direction.

The above layout of the magnets improves the density of magnetic fluxtoward the stator.

The thirty-fourth disclosure relates to a rotating electrical machinewhich comprises: (a) a rotor which includes a magnet unit and isretained to be rotatable; and (b) a stator which is equipped with astator winding made up of a plurality of phase windings, the statorbeing arranged coaxially with the rotor. The stator winding includesmagnet facing portions which overlap the magnet unit in an axialdirection and turns each of which joints a first one and a second one ofthe magnet facing portions used for the same phase together axiallyoutside the magnet unit. The first and second ones of the magnet facingportions are away from each other with a given number of the magnetfacing portions interposed therebetween. The first and second ones ofthe magnet facing portions which are used for the same phase and joinedtogether by one of the turns are arranged on the same pitch circledefined about a center of the rotor. If an arrangement pitch that is aninterval between centers of the circumferentially adjacent magnet facingportions arranged on the same pitch circle in the circumferentialdirection is defined as Ps, a diameter of the same pitch circle isdefined as Ds, and Ds/Ps is expressed by τ, a relation of 24<τ<34 ismet.

A rotating electrical machine, as disclosed in the above patentliterature 4, is known which includes a rotor which is equipped with amagnet unit and retained to be rotatable and a stator which is equippedwith a stator winding made up of a plurality of phase windings andarranged coaxially with the rotor. The stator winding includes magnetfacing portions located to overlap the magnet unit in the axialdirection and turns each of which joints a first one and a second one ofthe magnet facing portions used for the same phase together axiallyoutside the magnet unit. The first and second ones of the magnet facingportions are away from each other with a given number of the magnetfacing portions interposed therebetween.

In order to strengthen torque output by the rotating electrical machine,it is required to select the arrangement pitch between the magnet facingportions of the stator winding to be a suitable value in thecircumferential direction. The pitch usually depends upon the size ofthe rotating electrical machine. It is, thus, necessary to determine thepitch in view of the size of the rotating electrical machine, thusresulting in an increase in number of design steps.

It is, therefore, a principal object of the thirty-fourth disclosure toprovide a rotating electrical machine which is capable of suitablydetermine the arrangement pitch of the magnet facing portions to avoidan increase in designing step thereof. In the thirty-fourth disclosure,the magnet facing portions which are used for the same phase and joinedtogether by the turns are arranged on the same pitch circle definedabout the axis of the rotor. An interval between the centers of themagnet facing portions which are arranged adjacent each other in thecircumferential direction on the same pitch circle is defined as thearrangement pitch Ps. The diameter of the same pitch circle is definedas Ds which depends upon the size of the rotating electrical machine.The inventors of this application have found that if Ds/Ps is expressedby τ, a suitable increase in torque output may be achieved regardless ofthe size of the rotating electrical machine by selecting the value τ tolie in a suitable range, and that such a range meets a relation of24<τ<34.

In the thirty-fourth disclosure, the arrangement pitch of the magnetfacing portions is, therefore, selected to meet a relation of 4<τ<34 inthe circumferential direction. The use of the value τ enables the numberof the designing steps to be properly minimized.

The magnet facing portions and the turns are sometimes made fromconductive material other than copper. In such a case, if the electricalresistivity [Ωm] of copper is defined as ρ1, an electrical resistivityof the conductive material is defined as ρ2, and ρ1/ρ2 is expressed byρs, a relation of 24/ρs<τ<34/ρs is preferably met. For instance, in acase of use of conductive material (e.g., aluminum) which is higher inelectrical resistivity than copper, ρ1 will be one or less, so that alower limit or an upper limit of τ becomes great. This means that in acase of use of conductive material higher in electrical resistivity thancopper, the arrangement pitch is shorter than that in a case of use ofcopper. The above described thirty-fifth disclosure avoids an increasein number of designing steps even when the magnet facing portions andthe turns are made from conductive material other than copper.

The number of pole pairs of the rotor may be selected to be 12 or more.

The thirty-sixth disclosure relates to the structure, as set forth inthe thirty-fourth or the thirty-fifth disclosure, wherein there of notooth made from soft magnetic material between the circumferentiallyadjacent magnet facing portions.

The thirty-sixth disclosure relates to the slot-less structure in whicha tooth made from soft magnetic material is not arranged between thecircumferentially adjacent magnet facing portions. A sectional area ofthe conductors may, therefore, be increased by placing the magneticfacing portions close to each other as compared with a tooth is disposedbetween the magnet facing portions. The slot-less structure has no corebetween the magnet facing portions, thereby eliminating a risk ofmagnetic saturation. The increased sectional area of the conductors andthe elimination of the risk of magnetic saturation enable an amount ofelectrical current delivered to the stator winding to be increase,thereby achieving a structure suitable for enhancing the torque outputfrom the rotating electrical machine.

The structure in which there is a tooth between the circumferentialadjacent conductors means that each tooth has a given thickness in theradial direction and a given width in the circumferential direction toform a portion of a magnetic circuit between the conductors, that is, amagnet-produced magnetic path. In contrast, the structure in which thereis no tooth between the conductors means that the above magnetic circuitis not created.

The slot-less structure may be implemented by a structure in thethirty-seventh disclosure. The thirty-seventh disclosure relates to arotating electrical machine which comprises: (a) a rotor which includesa magnet unit and is retained to be rotatable; and (b) a stator which isequipped with a stator winding made up of a plurality of phase windings,the stator being arranged coaxially with the rotor. The stator windingincludes magnet facing portions which overlap the magnet unit in anaxial direction and turns each of which joints a first one and a secondone of the magnet facing portions used for the same phase togetheraxially outside the magnet unit. The first and second ones of the magnetfacing portions are away from each other with a given number of themagnet facing portions interposed therebetween. The first and secondones of the magnet facing portions which are used for the same phase andjoined together by one of the turns are arranged on the same pitchcircle defined about a center of the rotor. The magnet unit includes aplurality of magnets which are disposed on a surface of the rotor whichfaces the stator and have magnetic poles arrayed alternately in acircumferential direction. Winding-to-winding members are each disposedbetween the magnetic facing portions arranged adjacent each other in thecircumferential direction. If a width of the winding-to-winding membersenergized by excitation of the stator winding in the circumferentialdirection within a portion of the magnet unit equivalent to one ofmagnetic poles thereof is defined as Wt, a saturation magnetic fluxdensity of the winding-to-winding members is defined as Bs, a width ofthe magnet unit equivalent to one of the magnetic poles in thecircumferential direction of the magnet unit is defined as Wm, and theremanent flux density in the magnet unit is defined as Br, thewinding-to-winding members are made of magnetic material meeting arelation of Wt×Bs≤Wm×Br or non-magnetic material.

The thirty-seventh disclosure enables the stator to receive a sufficientamount of magnetic flux from the rotor.

In the thirty-seventh disclosure, the stator includes a stator core. Thestator core is located on one of radially opposed sides of the statorwinding which faces away from the rotor. The stator core includes a yokelocated on one of the radially opposed sides of the stator winding whichfaces away from the rotor and protrusions each of which extends into agap between the circumferentially adjacent magnet facing portions. Thethickness of each of the protrusions from the yoke in the radialdirection may be selected to be smaller than half a thickness of one ofthe magnet facing portions which is arranged adjacent the yoke in theradial direction.

The thirty-eighth disclosure relates to the structure, as set forth inthe thirty-sixth or the thirty-seventh disclosure, wherein the statorincludes a stator core. The stator core is located on an opposite sideof the stator winding to the rotor in a radial direction.

In the thirty-eighth disclosure, the stator core is assembled with thestator winding. A core made from soft magnetic material does not occupya gap between the circumferentially adjacent magnet facing portions. Inthis case, the stator core which is arranged on the opposite side to therotor functions as a back yoke, thereby creating a required magneticcircuit even when there is no core between the magnet facing portions.

The thirty-ninth disclosure relates to the structure, as set forth inthe thirty-fourth or the thirty-fifth disclosure, wherein the statorincludes a stator core. The stator core is located on an opposite sideof the stator winding to the rotor in a radial direction. The statorcore includes a yoke located on the opposite side of the stator windingto the rotor in the radial direction and protrusions which protrude fromthe yoke toward an interval between the circumferentially adjacentmagnet facing portions. The thickness of each of the protrusions fromthe yoke in the radial direction is smaller than half a thickness of themagnet facing portion in the radial direction.

In the thirty-ninth disclosure, the stator core has the protrusions eachof which projects from the yoke arranged farther away from the rotor inthe radial direction toward an interval between the circumferentiallyadjacent magnet facing portions. The protrusions have a thickness whichis smaller than half that of the magnet facing portions in the radialdirection. In this case, the protrusions have the thickness restrictedin the radial direction, so that the interval between thecircumferentially adjacent magnet facing portions does not function as atooth. The rotating electrical machine in the thirty-ninth disclosureis, therefore, designed to have the slot-less structure. This minimizesa risk of magnetic saturation thereby enabling an amount of electricalcurrent delivered to the stator winding to be increased. This creates astructure suitable for enhancing the torque output from the rotatingelectrical machine.

The thirty-ninth disclosure may be modified to have a structure in, forexample, the fortieth disclosure which relates to the structure, as setforth in the thirty ninth disclosure, wherein the magnet facing portionsare arranged at a given interval away from each other in acircumferential direction of the stator winding and stacked in amulti-layer form in a radial direction of the stator winding. Thethickness of each of the protrusions from the yoke in the radialdirection is set smaller than half a thickness of one of the magnetfacing portions which is arranged adjacent the yoke in the radialdirection.

The fortieth disclosure may be modified to have a structure in theforty-first disclosure. The forty-first disclosure relates to thestructure, as set forth in the fortieth disclosure, wherein theprotrusions engage the magnet facing portions in the circumferentialdirection.

The structure in the forty-first disclosure enables the magnet facingportions of the stator winding to be used as a positioner and arrangedin the circumferential direction.

The forty-second disclosure relates to the structure, as set forth inthe thirty-ninth disclosure, wherein one of the phase windings for thesame phase is made of a plurality of conductors connected electricallytogether, each of the conductors including the magnet facing portionsand turns. The stator core has more protrusions than the conductors.Each of the protrusions is arranged at a location on the stator whichcorresponds to a location of one of the conductors.

The structure in the forty-second disclosure facilitates positioning ofthe conductors in the circumferential direction in a case where each ofthe phase windings is made up of the plurality of conductors.

The forth-third disclosure relates to the structure, as set forth in anyone of the thirty-sixth to the forty-second disclosure, wherein thestator winding is made of a conductor having a flattened cross sectionwhose thickness in a radial direction is smaller than a width thereof ina circumferential direction.

In the forty-third disclosure, the conductor of the stator winding isdesigned in a flattened shape to have a thickness decreased in theradial direction of the magnet facing portions, thereby enabling thecenters of the magnet facing portions in the radial direction to bearranged close to the magnet unit of the rotor. This minimizes themagnetic saturation occurring in the stator of the slot-less structureand increases the density of magnetic flux in the magnetic facingportions of the stator winding to increase the torque output.

The forty-fourth disclosure relates to the structure, as set forth inany one of the thirty-sixth to the forty-third disclosure, wherein theconductor used in the stator winding includes a conductor body made ofan aggregation of twisted wires.

In the slot-less structure, a magnetic field produced by the magnet unitof the rotor will be applied directly to the conductors of the statorwinding through air. The magnetic field generated by the magnet unit ofthe rotor will be a rotating field because the rotor mechanicallyrotates. The strength of magnetic field, as viewed from the statorwinding, will be that of an ac magnetic field in the shape of a sinewave. The rotating magnetic field may contain a harmonic componenthigher than a fundamental frequency synchronizing with a frequency atwhich the rotor mechanically rotates.

The electrical resistance of the conductor is much smaller than that ofair. This causes an ac magnetic field containing a harmonic component tointerlink with the conductors, so that a harmonic electromotive force isgenerated which circulates in the conductors in proportion to a changein interlinkage magnetic flux with time. An eddy current resulting fromthe electromotive force flows through the conductor in the form of acirculating current, thereby generating eddy-current loss. This leads toan increase in temperature or mechanical vibration of the stator.

In order to alleviate the above problems, the structure in theforty-fourth disclosure has the conductors of the stator winding each ofwhich includes the conductor body made of an aggregation of twistedwires. This enables a current flow path defined by the conductor to bethin, thereby increasing an electrical resistance of the conductor to aflow of eddy current created when a magnetic field produced by themagnet unit containing a harmonic magnetic field interlinks with theconductor. This minimizes the eddy current flowing through theconductor.

Each conductor is made of an aggregation of twisted wires, so that eachof the wires has portions to which magnetic field is applied in oppositedirections, thereby cancelling back electromotive forces resulting fromthe interlinkage magnetic field. This enhances effects of decreasing theeddy current flowing in the conductors.

The forty-fifth disclosure relates to the structure, as set forth in theforty-fourth disclosure, wherein at least two of the wires which arearranged adjacent each other are electrically insulated from each other.

The structure in the forty-fifth disclosure enables an area of a currentloop through which an eddy current flows to be decreased to increaseeffects on decrease in eddy current.

The forty-sixth disclosure relates to the structure as set forth in theforty-fourth or the forty-fifth disclosure, wherein an electricalresistance to flow of electrical current between the adjacent wires ishigher than an electrical resistance of each of the wires to flow ofelectrical current through itself.

In the forty-sixth disclosure, each of the wires has the above property,i.e., electrical anisotropy. Each of the wires, therefore, serves toincrease effects of decreasing the eddy current even if each of thewires has not insulating layer on an outer periphery thereof.

The forty-seventh disclosure relates to the structure, as set forth inany one of the thirty-fourth to the forty-seventh disclosure, whereinthe turns are secured to at least axially opposed ends of the stator.

The structure in the forty-seventh disclosure achieves a firm joint ofthe stator winding to the stator.

In the forty-eighth disclosure, each of the turns has a sectional areagreater than that of the magnet facing portions.

A place located axially outside the magnet facing portions does not facethe magnet unit in the radial direction, so that space in which theturns are mounted is less restricted. Accordingly, the sectional area ofeach of the turns is selected to be greater than that of the magnetfacing portions, thereby decreasing the electrical resistance of theturns to enhance the torque output.

The fiftieth disclosure relates to a rotating electrical machine whichcomprises: (a) a rotor which includes a magnet unit and is retained tobe rotatable; and (b) a stator which is equipped with a stator windingincluding a plurality of conductors, the stator being arranged to facethe rotor. A core made from a soft magnetic material is not disposedbetween the circumferentially adjacent conductors. Each of theconductors includes a conductor made of an aggregation of twisted wires.

Rotating electrical machines are known which are, as taught in the abovepatent literature 5, used for household, industrial, game, farming,architectural, or automotive applications. Typically, a stator core(i.e., an iron core) has formed therein slots which are defined by teethand in which a winding is disposed. Conductors, such as copper wires oraluminum wires, are disposed in the slots to complete a stator winding.

Slot-less motors which omit the teeth from the stator have also beenproposed.

In the slot-less structure, a magnetic field produced by the magnet unitof the rotor will be applied directly to the conductors of the statorwinding through air. The magnetic permeability of the conductors isapproximately equal to that of air, so that a magnetic field isuniformly applied to air and the conductors. The magnetic fieldgenerated by the magnet unit of the rotor will be a rotating fieldbecause the rotor mechanically rotates. The strength of magnetic field,as viewed from the stator winding, will be that of an ac magnetic fieldin the shape of a sine wave. The rotating magnetic field may contain aharmonic component higher than a fundamental frequency synchronizingwith a frequency at which the rotor mechanically rotates.

The electrical resistance of the conductors is much smaller than that ofair. This causes an ac magnetic field containing a harmonic component tointerlink with the conductors, so that a harmonic electromotive force isgenerated which circulates in the conductors in proportion to a changein interlinkage magnetic flux with time. An eddy current resulting fromthe electromotive force flows through the conductor in the form of acirculating current, thereby generating eddy-current loss. This leads toan increase in temperature or mechanical vibration of the stator.

It is, therefore, a principal object of the fiftieth disclosure toprovide a slot-less structure of a rotating electrical machine which iscapable of reducing eddy current loss. The fiftieth disclosure relatesto the slot-less structure in which a tooth made from soft magneticmaterial is not disposed between the circumferentially adjacentconductors. In order to alleviate the above problems, the structure inthe fiftieth disclosure has the conductors of the stator winding each ofwhich includes the conductor body made of an aggregation of twistedwires. This enables a current flow path defined by the conductors to bethin, thereby increasing effects of the conductors on decrease in eddycurrent even when a magnetic field produced by the magnet unitcontaining a harmonic magnetic field interlinks with the conductors.This minimizes the eddy current flowing through the conductors todecrease the eddy-current loss.

Each conductor is made of an aggregation of twisted wires, so that eachof the wires has portions to which magnetic field is applied in oppositedirections, thereby cancelling back electromotive forces resulting fromthe interlinkage magnetic field. This enhances effects on decrease ineddy current flowing in the conductors to increase the effects ondecrease in eddy-current loss.

The structure in which the teeth are respectively disposed between theconductors arrayed in the circumferential direction means that each ofthe teeth has a given thickness in the radial direction and a givenwidth in the circumferential direction of the stator, so that a portionof the magnetic circuit, that is, a magnet magnetic path lies betweenthe adjacent conductors. In contrast, the structure in which no toothlies between the adjacent conductors means that there is no magneticcircuit described above.

The fifty-first disclosure relates to a rotating electrical machinewhich comprises: (a) a rotor which includes a magnet unit and isretained to be rotatable; and (b) a stator which is equipped with astator winding made up of a plurality of conductors and a stator core.The stator is arranged to face the rotor. The conductors include magnetfacing portions arranged to face the magnet unit in a radial directionand turns each of which joints a first one and a second one of themagnet facing portions used for the same phase together axially outsidethe magnet facing portions. The first and second ones of the magnetfacing portions are arranged away from each other with a given number ofthe magnet facing portions interposed therebetween. The first and secondones of the magnet facing portions which are used for the same phase andjoined together by one of the turns are arranged on the same pitchcircle defined about a center of the rotor. The stator core includes ayoke located on the opposite side of the stator winding to the rotor inthe radial direction and protrusions which protrude from the yoke towardan interval between the circumferentially adjacent magnet facingportions. The thickness of each of the protrusions from the yoke in theradial direction is smaller than half a thickness of the magnet facingportion in the radial direction. Each of the conductors includes aconductor body made of an aggregation of twisted wires.

In the fifty-first disclosure, the stator core has the protrusions eachof which projects from the yoke arranged farther away from the rotor inthe radial direction toward an interval between the circumferentiallyadjacent magnet facing portions. The protrusions have a thickness whichis smaller than half that of the magnet facing portions in the radialdirection. In this case, the protrusions have the thickness restrictedin the radial direction, so that the interval between thecircumferentially adjacent magnet facing portions does not function as atooth. The rotating electrical machine in the fifty-first disclosure is,therefore, designed to have the slot-less structure.

Since the thickness of the protrusions is restricted in the radialdirection, the amount of interlinkage magnetic flux, as produced by themagnet unit, passing through portions of the magnet facing portionsextending outside the protrusions in the radial direction is increased.Such an increase will result in an increase in eddy current. However, inthe fifty-first disclosure, each of the conductors of the stator windingis made of twisted wires, thereby enhancing effects on decrease in eddycurrent flowing through the conductors. This results in a decrease ineddy current to reduce the eddy-current loss and also achieves apositioning function.

The structure in the fifty-first disclosure may be modified to have thestructure in the fifty-second disclosure. In the fifty-seconddisclosure, the magnet facing portions are arranged at a given intervalaway from each other in a circumferential direction of the statorwinding and stacked in a multi-layer form in a radial direction of thestator winding. The thickness of each of the protrusions from the yokein the radial direction is smaller than half a thickness of one of themagnet facing portions which is arranged adjacent the yoke in the radialdirection.

The structure in the fifty-second disclosure may be modified to have thestructure in the fifty-third disclosure. In the fifty-third disclosure,the protrusions engage the magnet facing portions in a circumferentialdirection.

The structure in the fifth-third disclosure enables the protrusions tobe used as positioners for the magnet facing portions of the statorwinding to arrange the magnet facing portions in the circumferentialdirection.

The slot-less structure may be designed to have a structure in thefifth-fourth disclosure. Specifically, the structure of the fifth-fourthdisclosure relates to a rotating electrical machine which comprises: (a)a stator which is equipped with a stator winding made up of a pluralityof conductors; and (b) a rotor which is equipped with a magnet unitdisposed on a surface thereof facing the stator. The rotor is retainedto be rotatable. The conductors include magnet facing portions arrangedto face the magnet unit in a radial direction and turns each of whichjoints a first one and a second one of the magnet facing portions usedfor the same phase together axially outside the magnet facing portions.The first and second ones of the magnet facing portions are arrangedaway from each other with a given number of the magnet facing portionsinterposed therebetween. The magnet facing portions of the statorwinding are arranged at a given interval away from each other in thecircumferential direction. The magnet unit includes a plurality ofmagnets which are disposed on a surface of the rotor which faces thestator and have magnetic poles arrayed alternately in thecircumferential direction. The stator is equipped withwinding-to-winding members each of which is disposed between themagnetic facing portions arranged adjacent each other in thecircumferential direction. If a width of the winding-to-winding membersenergized by excitation of the stator winding in the circumferentialdirection within a portion of the magnet unit equivalent to one ofmagnetic poles thereof is defined as Wt, a saturation magnetic fluxdensity of the winding-to-winding members is defined as Bs, a width ofthe magnet unit equivalent to one of the magnetic poles in thecircumferential direction of the magnet unit is defined as Wm, and theremanent flux density in the magnet unit is defined as Br, thewinding-to-winding members are made of magnetic material meeting arelation of Wt×Bs≤Wm×Br or non-magnetic material.

The structure in the fifty-fourth disclosure enables the stator tosufficiently receive magnetic flux produced by the magnet unit of therotor.

The fifty-fifth disclosure relates to the structure, as set forth in anyone of the fiftieth to the fifty-fourth disclosure, wherein each of thewires is made of conducive fibers.

The structure in the fifty-fifth disclosure has the wires each of whichis made of conductive fibers. This enables a current flow path definedby the conductors to be thin, thereby enabling the number of times thecurrent flow path is twisted to be increased. This increases effects ondecrease in eddy current to enhance effects on decrease in eddy-currentloss.

Each of the wires may be, as in the fifty-sixth disclosure, made ofcarbon nanotube fibers (which will also be referred to below as CNT).This more effectively increases the effects on decrease in eddy currentto decrease the eddy-current loss.

Each of the wires may be, as in the fifty-seventh disclosure, made ofcarbon nanotube fibers which include boron-containing microfibers inwhich at least a portion of carbon is substituted with boron. This moreeffectively strengthens the effects that decrease eddy current, todecrease the eddy-current loss.

The fifty-eighth disclosure relates to the structure, as set forth inany one of the fiftieth disclosure to the fifty-seventh disclosure,wherein the stator winding is made of a conductor having a flattenedcross section whose thickness in a radial direction is smaller than awidth thereof in a circumferential direction.

In the fifth-eighth disclosure, the conductor of the stator winding isdesigned in a flattened shape to have a thickness decreased in theradial direction of the magnet facing portions, thereby enabling thecenters of the magnet facing portions in the radial direction to bearranged close to the magnet unit of the rotor. This minimizes themagnetic saturation occurring in the stator using the slot-lessstructure and increases the density of magnetic flux in the magneticfacing portions of the stator winding to increase the torque output.

The flattened shape of the conductors enhances the torque output, buthowever, results in an increase in amount of magnetic flux interlinkingwith the conductors. Such an increase will result in an increase in eddycurrent. However, in the fifth-eighth disclosure, each of the conductorsof the stator winding is made of an aggregation of twisted wires,thereby enhancing effects on decrease in eddy current flowing throughthe conductors. The flattened shape of the conductors to have athickness decreased in the radial direction also serves to reduce theeddy current. The structure in the fifty-eighth disclosure, therefore,serves to enhance the torque output from the rotating electrical machineand reduce the eddy current.

The structure of the fifth-eighth disclosure may be designed to have thestator equipped with a stator core. The stator core may be located on anopposite side of the stator winding to the rotor in the radialdirection. In this case, the size of an air gap between the stator coreand the rotor may be decreased by shaping the conductors to be flat tohave a thickness of the magnet facing portions decreased in the radialdirection. This reduces the magnetic resistance of a magnetic circuit toa flow of magnetic flux passing through the stator and the rotor toincrease the amount of magnetic flux in the magnetic circuit. Thisminimizes magnetic saturation occurring in the stator using theslot-less structure and increases the torque output from the rotatingelectrical machine.

The fifty-ninth disclosure relates to the structure, as set forth in anyone of the fiftieth to fifty-eighth disclosure, wherein the magnet unitincludes permanent magnets.

In a structure in which the magnet unit is equipped with a fieldwinding, when drive control for the rotating electrical machine is notperformed, it will cause not current to be delivered to the fieldwinding, so that the field winding does not produce magnetic flux. Incontrast, in a case where the magnet unit is equipped with permanentmagnets, the magnetic field is created by the permanent magnets all thetime. Accordingly, when power is transmittable from a rotating shaft ofthe rotating electrical machine to wheels of a vehicle, it will causethe rotor to be rotated by the wheels even when the rotating electricalmachine is at rest, so that the magnet unit generates a rotatingmagnetic field all the time, thereby causing eddy current flowingthrough the conductors to be created by a harmonic magnetic field. Thisresults in occurrence of eddy-current loss.

The structure in the fifty-ninth disclosure, however, has the conductorsof the stator winding each of which is made of an aggregation of aplurality of twisted wires, thereby enhancing effects on decrease ineddy current flowing through the conductors. The structure in thefifty-ninth disclosure, therefore, serves to effectively reduce theeddy-current loss when the rotating electrical machine is at rest.

The sixtieth disclosure relates to the structure, as set forth in thefifty-ninth disclosure, wherein the permanent magnets include firstmagnets whose magnetization direction extends in an arc shape toward acenter of a magnetic pole thereof and second magnets whose magnetizationdirection extends in an arc shape toward a center of a magnetic polethereof and which is different in polarity from that of the firstmagnets. The first magnets and the second magnets are arrangedalternately in the circumferential direction on a surface of the rotorwhich faces the stator.

A rotor of a rotating electrical machine of an embedded-magnet structureis known which has permanent magnets arranged on a d-axis and an ironcore arranged on a q-axis. Excitation of a stator winding near thed-axis will results flow of excited current from a stator to the q-axisof the rotor. This results in magnetic saturation in a wide range arounda portion of the core of the rotor on the q-axis.

In order to eliminate the magnetic saturation occurring in a portion ofthe core on the q-axis, the structure in the sixtieth disclosure isdesigned to have permanent magnets on a surface of the rotor which facesthe stator. Further, in order to enhance the torque output from therotating electrical machine, the structure of the sixtieth disclosureuses polar anisotropic permanent magnets. Specifically, the permanentmagnets include the first magnets whose magnetization direction extendsin an arc shape toward the center of the magnetic pole thereof and thesecond magnets whose magnetization direction extends in an arc shapetoward the center of the magnetic pole thereof and which is different inpolarity from that of the first magnets. The first magnets and thesecond magnets are arranged alternately in the circumferential directionon the surface of the rotor which faces the stator. This increases theamount of magnetic flux in the magnetic circuit and enhance the torqueoutput from the rotating electrical machine.

The increase in amount of magnetic flux will result in an increase intorque output, but however, it leads to an increase in amount ofmagnetic flux interlinking with the conductors. Such an increase willresult in an increase in eddy current. However, in the sixtiethdisclosure, each of the conductors of the stator winding is made oftwisted wires, thereby enhancing effects on decrease in eddy currentflowing through the conductors. The structure in the sixtiethdisclosure, therefore, serves to strengthen the torque produced by therotating electrical machine and reduce the eddy-current loss.

The permanent magnets in the sixtieth disclosure may alternatively bedesigned to have a structure in the sixty-first disclosure. In thesixty-first disclosure, the permanent magnets include first magnetswhose magnetization direction is oriented in a radial direction andsecond magnets whose magnetization direction is oriented in a directionother than the radial direction. The first magnets are arranged at agiven interval away from each other in the circumferential direction ona surface of the rotor which faces the stator. Each of the secondmagnets is disposed in the circumferentially adjacent first magnets.

The sixty-second disclosure relates to the structure, as set forth inany one of the fiftieth to sixty-first disclosure, wherein theconductors include magnet facing portions arranged to face the magnetunit in a radial direction and turns each of which joints a first oneand a second one of the magnet facing portions used for the same phasetogether axially outside the magnet facing portions. The first andsecond ones of the magnet facing portions are arranged away from eachother with a given number of the magnet facing portions interposedtherebetween. Each of the turns has a sectional area greater than thatof the magnet facing portions.

A place located axially outside the magnet facing portions does not facethe magnet unit in the radial direction, so that space in which theturns are mounted is less restricted. Accordingly, the sectional area ofeach of the turns is selected to be greater than that of the magnetfacing portions, thereby decreasing the electrical resistance of theturns to enhance the torque output.

A magnetic flux leaking from the rotating magnetic field interlinks withthe turns. The turns have an increased sectional area, thus leading to arisk that the eddy current may become great. However, in thesixty-second disclosure, each of the conductors of the stator winding ismade of an aggregation of twisted wires, thereby enhancing effects ondecrease in eddy current flowing through the conductors. The structurein the sixty-second disclosure, therefore, serves to enhance the torqueoutput from the rotating electrical machine and reduce the eddy-currentloss.

The sixty-third disclosure relates to a rotating electrical machinewhich comprises: (a) a rotor which includes a magnet unit and isretained to be rotatable; and (b) a stator which is equipped with astator winding made up of a plurality of conductors. The stator isarranged coaxially with the rotor. A tooth made of soft magneticmaterial is not disposed between the circumferentially adjacentconductors. A distance between a surface of the magnet unit which facesthe stator in a radial direction and an axial center of the rotor in theradial direction is set to be 50 mm or more. If a distance between asurface of the magnet unit facing away from the stator and a surface ofthe stator winding which faces away from the rotor in the radialdirection is defined as LS, and a thickness of the magnet unit in theradial direction is defined as LM, LM/LS is selected to be greater thanor equal to 0.6 and smaller than or equal to 1.0. If a maximum value ofa distance from an axial center of the rotor in the radial direction isdefined as a first distance MA, a minimum distance from the axial centerof the rotor in the radial direction is defined as a second distance MBin a magnetic circuit in the stator and the rotor, MB/MA is selected tobe 0.7 or more and 1.0 or less.

As a conventional brushless rotating electrical machine, a core-lessmotor taught in the above patent literature or a slot-less motor inwhich an iron core is not used with a stator is widely known.

A small-sized slot-less structure of a rotating electrical machine whoseoutput is several tens or hundreds watt is usually used for models. Theinventors of this application have not seen examples where the slot-lessstructure is used with large-sized industrial rotating electricalmachines whose output is more than 10 kW. The inventors have studied thereason for this.

Modern major rotating electrical machines are categorized into four maintypes: a brush motor, a squirrel-cage induction motor, a permanentmagnet synchronous motor, a reluctance motor.

Brush motors are supplied with exciting current using brushes.Large-sized brush motors, therefore, have an increased size of brushes,thereby resulting in complex maintenance thereof. With the remarkabledevelopment of semiconductor technology, brushless motors, such asinduction motors, have been used instead. In the field of small-sizedmotors, a large number of coreless motors have also come on the marketin terms of low inertia or economic efficiency.

Squirrel-cage induction motors operate on the principle that a magneticfield produced by a primary stator winding is received by a secondarystator core to deliver induced current to bracket-type conductors,thereby creating magnetic reaction field to generate torque. In terms ofsmall-size and high-efficiency of the motors, it is inadvisable that thestator and the rotor be designed not to have iron cores.

Reluctance motors are motors designed to use a change in reluctance inan iron core. It is, thus, inadvisable that the iron core be omitted inprinciple.

In recent years, permanent magnet synchronous motors have used an IPM(Interior Permanent Magnet) rotor. Especially, most large-sized motorsuse an IPM rotor unless there are special circumstances.

IPM motors has properties of producing both magnet torque and reluctancetorque. The ratio between the magnet torque and the reluctance torque istimely controlled using an inverter. For these reasons, the IMP motorsare thought of as being compact and excellent in ability to becontrolled.

According to analysis by the inventors, torque on the surface of a rotorproducing the magnet torque and the reluctance torque is expressed inFIG. 73 as a function of the distance DM between a surface of one ofradially opposed sides of the permanent magnets of the rotor which facesthe stator and the center of the axis of the rotor, that is, the radiusof a stator core of a typical inner rotor indicated on the horizontalaxis.

The potential of the magnet torque, as can be seen in the followingequation (eq1), depends upon the strength of magnetic field created by apermanent magnet, while the potential of the reluctance torque, as canbe seen in the following equation (eq2), depends upon the degree ofinductance, especially, on the q-axis.The magnet torque=k·Ψ·Iq  (eq1)The reluctance torque=k·(Lq−Ld)·Iq·Id  (eq2)

Comparison between the strength of magnetic field produced by thepermanent magnet and the degree of inductance of a winding using theradius of the stator core shows that the strength of magnetic fieldcreated by the permanent magnet, that is, the amount of magnetic flux Ψis proportional to a total area of a surface of the permanent magnetwhich faces the stator. In case of a cylindrical stator, such a totalarea is a cylindrical surface area of the permanent magnet. Technicallyspeaking, the permanent magnet has an N-pole and an S-pole, and theamount of magnetic flux Ψ is proportional to half the cylindricalsurface area. The cylindrical surface area is proportional to the radiusof the cylindrical surface and the length of the cylindrical surface.When the length of the cylindrical surface is constant, the cylindricalsurface area is proportional to the radius of the cylindrical surface.

The inductance Lq of the winding depends upon the shape of the ironcore, but its sensitivity is low and rather proportional to the squareof the number of turns of the stator winding, so that it is stronglydependent upon the number of the turns. The inductance L is expressed bya relation of L=μ·N{circumflex over ( )}2×S/δ where μ is permeability ofa magnetic circuit, N is the number of turns, S is a sectional area ofthe magnetic circuit, and δ is an effective length of the magneticcircuit. The number of turns of the winding depends upon the size ofspace occupied by the winding. In the case of a cylindrical motor, thenumber of turns, therefore, depends upon the size of space occupied bythe winding of the stator, in other words, areas of slots in the stator.The slot is, as demonstrated in FIG. 74 , rectangular, so that the areaof the slot is proportional to the product of a and b where a is thewidth of the slot in the circumferential direction, and b is the lengthof the slot in the radial direction.

The width of the slot in the circumferential direction becomes largerwith an increase in diameter of the cylinder, so that the width isproportional to the diameter of the cylinder. The length of the slot inthe radial direction is proportional to the diameter of the cylinder.The area of the slot is, therefore, proportional to the square of thediameter of the cylinder. It is apparent from the above equation (eq2)that the reluctance torque is proportional to the square of current inthe stator. The performance of the rotating electrical machine,therefore, depends upon how much current is enabled to flow in therotating electrical machine, that is, depends upon the areas of theslots in the stator. The reluctance is, therefore, proportional to thesquare of the diameter of the cylinder for a cylinder of constantlength. Based on this fact, a relation of the magnetic torque and thereluctance torque with the radius of the stator core is shown by plotsin FIG. 73 .

The magnet torque is, as shown in FIG. 73 , increased linearly as afunction of the radius of the stator core, while the reluctance torqueis increased in the form of a quadratic function as a function of theradius of the stator core. FIG. 73 shows that when the radius of thestator core is small, the magnetic torque is dominant, while thereluctance torque becomes dominant with an increase in radius of thestator core. The inventors of this application have arrived at theconclusion that an intersection of lines expressing the magnetic torqueand the reluctance torque in FIG. 73 lies near a stator core radius of50 mm. It seems that it is difficult for a motor whose output is 10 kWand whose stator core has a radius much larger than 50 mm to omit thestator core because the use of the reluctance torque is now mainstream.This is one of reasons why the slot-less structure is not used inlarge-sized motors.

The rotating electrical machine using an iron core in the stator alwaysfaces a problem associated with the magnetic saturation of the ironcore. Particularly, radial gap type rotating electrical machines has alongitudinal section of the rotating shaft which is of a fan shape foreach magnetic pole, so that the further inside the rotating electricalmachine, the smaller the width of a magnetic circuit, so that innerdimensions of teeth forming slots in the core become a factor of thelimit of performance of the rotating electrical machine. Even if a highperformance permanent magnet is used, generation of magnetic saturationin the permanent magnet will lead to a difficulty in producing arequired degree of performance of the permanent magnet. It is necessaryto design the permanent magnet to have an increased inner diameter inorder to eliminate a risk of generation of the magnetic saturation,which results in an increase in size of the rotating electrical machine.

For instance, a typical rotating electrical machine with a distributedthree-phase winding is designed so that three to six teeth serve toproduce a flow of magnetic flux for each magnetic pole, but encounters arisk that the magnetic flux may concentrate on a leading one of theteeth in the circumferential direction, thereby causing the magneticflux not to flow uniformly in the three to six teeth. For instance, theflow of magnetic flux concentrates on one or two of the teeth, so thatthe one or two of the teeth in which the magnetic saturation isoccurring will move in the circumferential direction with rotation ofthe rotor, which may lead to a factor causing the slot ripple.

For the above reasons, it is required to omit the teeth in the slot-lessstructure of the rotating electrical machine in which the radius of thestator core is 50 mm or more to eliminate the risk of generation of themagnetic saturation. The omission of the teeth, however, results in anincrease in magnetic resistance in magnetic circuits of the rotor andthe stator, thereby decreasing torque produced by the rotatingelectrical machine. The reason for such an increase in magneticresistance is that there is, for example, a large air gap between therotor and the stator. The slot-less structure of the rotating electricalmachine in which the radius of the stator core is 50 mm or more,therefore, has room for improvement for increasing the output torque.

It is a principal object of the sixty-third disclosure to provide arotating electrical machine which is of a slot-less structure in whichthe above described DM is 50 mm or more and capable of enhancing thedegree of torque output.

In the sixty-third disclosure, the more the above value of LM/LS, thegreater the thickness of the magnet unit in the radial direction,thereby increasing the degree of magnetomotive force produced by thepermanent magnets. This enables the slot-less structure of the rotatingelectrical machine to increase the magnetic flux density in the statorwinding to enhance the torque output therefrom. The higher the value ofLM/LS, the smaller the size of the gap between the rotor and the statorwinding, thereby resulting in a decrease in magnetic resistance in themagnetic circuit in the rotor and the stator. This enables the torqueoutput to be increased. In the sixty-third disclosure, the value ofLM/LS is selected to be 0.6 or more, which is capable of achieving astructure suitable for enhancing the torque output.

Further, in the sixty-third disclosure, if a maximum value of a distancefrom an axial center of the rotor in the radial direction in a magneticcircuit of the rotor and the stator is defined as a first distance MA, aminimum distance from the axial center of the rotor in the radialdirection in the magnetic circuit is defined as a second distance MB, avalue of MB/MA is selected to be greater than or equal to 0.7 andsmaller than or equal to 1.0. The greater value of MB/MA means that thethinning of the magnetic circuit in the radial direction. The thinningof the magnetic circuit in the radial direction means the magnetic pathis shortened, thus resulting in a decrease in magnetic resistance.Accordingly, the structure suitable to decrease the magnetic resistanceis achieved by selecting the value of MB/MA to be 0.7 or more. Thisenhances the torque output.

The structure in which there is no tooth between the conductors arrangedin the circumferential direction means that the tooth has a giventhickness in the radial direction and a given width in thecircumferential direction, and a portion of the magnetic circuit, i.e.,a magnet-produced magnetic path is formed between the conductors. Inthis respect, the structure in which there are no teeth also means thatthe above described magnetic circuit is not created.

The slot-less structure of the rotating electrical machine may bedesigned to have a structure in the sixty-fourth disclosure. Thesixty-fourth disclosure relates to a rotating electrical machine whichcomprises: (a) a stator which is equipped with a stator winding made upof a plurality of conductors; and (b) a rotor which is equipped with amagnet unit disposed on a surface thereof facing the stator, the rotorbeing retained to be rotatable. The conductors include magnet facingportions arranged to face the magnet unit in a radial direction andturns each of which joints a first one and a second one of the magnetfacing portions used for the same phase together axially outside themagnet facing portions. The first and second ones of the magnet facingportions are arranged away from each other with a given number of themagnet facing portions interposed therebetween. The magnet facingportions of the stator winding are arranged at a given interval awayfrom each other in a circumferential direction. The magnet unit includesa plurality of magnets which are disposed on a surface of the rotorwhich faces the stator and have magnetic poles arrayed alternately inthe circumferential direction. The stator is equipped withwinding-to-winding members each of which is disposed between themagnetic facing portions arranged adjacent each other in thecircumferential direction. If a width of the winding-to-winding membersenergized by excitation of the stator winding in the circumferentialdirection within a portion of the magnet unit equivalent to one ofmagnetic poles thereof is defined as Wt, a saturation magnetic fluxdensity of the winding-to-winding members is defined as Bs, a width ofthe magnet unit equivalent to one of the magnetic poles in thecircumferential direction of the magnet unit is defined as Wm, and theremanent flux density in the magnet unit is defined as Br, thewinding-to-winding members are made of magnetic material meeting arelation of Wt×Bs≤Wm×Br or non-magnetic material.

The structure in the sixty-fourth disclosure has the stator sufficientlyreceiving magnetic flux produced by the magnet unit of the rotor.

The slot-less structure of the rotating electrical machine may bedesigned to have a structure in the sixty-sixth disclosure. Thesixty-sixth disclosure relates to a rotating electrical machine whichcomprises: (a) a rotor which includes a magnet unit and is retained tobe rotatable; and (b) a stator which is equipped with a stator windingincluding a plurality of conductors and a stator core. The stator isarranged coaxially with the rotor. A distance between a surface of themagnet unit which faces the stator in a radial direction and an axialcenter of the rotor in the radial direction is set to be 50 mm or more.The conductors include magnet facing portions arranged to face themagnet unit in a radial direction and turns each of which joints a firstone and a second one of the magnet facing portions used for the samephase together axially outside the magnet facing portions. The first andsecond ones of the magnet facing portions are arranged away from eachother with a given number of the magnet facing portions interposedtherebetween. The first and second ones of the magnet facing portionswhich are used for the same phase and joined together by one of theturns are arranged on the same pitch circle defined about a center ofthe rotor. The stator core includes a yoke located on an opposite sideof the stator winding to the rotor in the radial direction andprotrusions which protrude from the yoke toward an interval between thecircumferentially adjacent magnet facing portions. The thickness of eachof the protrusions from the yoke in the radial direction is smaller thanhalf a thickness of the magnet facing portion in the radial direction.

In the sixty-sixth disclosure, the stator core is equipped with theprotrusions each of which extends from the yoke toward a gap between thecircumferentially adjacent magnet facing portions. The thickness of eachof the protrusions from the yoke in the radial direction is smaller thanhalf the thickness of one of the magnet facing portions which isarranged adjacent the yoke in the radial direction. In this case, eachof the magnet facing portions of the stator winding may be arranged inthe circumferential direction with use of the protrusions aspositioners. Since the thickness of the protrusions is restricted in theradial direction, the protrusions do not serve as teeth between thecircumferentially adjacent magnet facing portions. The rotatingelectrical machine in the sixty-sixth disclosure is, therefore, of theslot-less structure.

The structure in the sixty-sixth disclosure may be designed to have astructure in the sixty-seventh disclosure. In the sixty-seventhdisclosure, the magnet facing portions are arranged at a given intervalaway from each other in a circumferential direction of the statorwinding and stacked in a multi-layer form in a radial direction of thestator winding. The thickness of each of the protrusions from the yokein the radial direction is smaller than half the thickness of one of themagnet facing portions which is arranged adjacent the yoke in the radialdirection.

The structure in the sixty-seventh disclosure may be designed to have astructure in the sixty-eighth disclosure. In the sixty-eighthdisclosure, the protrusions engage the magnet facing portions in thecircumferential direction.

The structure in the sixty-eighth disclosure is capable of arranging themagnet facing portions of the stator winding in the circumferentialdirection with use of the protrusions as positioners.

The sixty-ninth disclosure relates to the structure, as set forth in anyone of the sixty-fifth to the sixty-eighth disclosure, wherein thestator is equipped with a stator core which is arranged on one ofradially opposed sides of the stator winding which is located fartheraway from the rotor.

In the sixty-ninth disclosure, the stator core which is arranged on theopposite side to the rotor in the radial direction functions as a backyoke, thereby creating a required magnetic circuit even when there is notooth between the magnet facing portions.

The seventieth disclosure relates to the structure, as set forth in anyone of the sixty-fifth to the sixty-eighth disclosure, wherein the rotoris arranged radially outside the stator. The magnet unit includes firstmagnets whose magnetization direction extends in an arc-shape toward thecenter of a magnetic pole thereof and second magnets whose magnetizationdirection extends in an arc-shape toward the center of a magnetic polethereof. The first magnets are different in magnetic polarity than thesecond magnets. The first magnets and the second magnets are arrangedalternately in the circumferential direction on a surface of the rotorwhich faces the stator. The first distance is a distance between theaxial center of the rotor and a radially outer surface of the annularmagnet unit in the radial direction. The second distance is a distancebetween the axial center of the rotor and a radially inner surface ofthe annular stator core in the radial direction.

In the seventieth disclosure, the rotor is of an outer rotor structurein which the rotor is arranged radially outside the stator. The seconddistance is, therefore, set to a distance between the axial center ofthe rotor and a radially inner surface of the stator core in the radialdirection.

The structure in the seventieth disclosure uses polar anisotropicpermanent magnets in order to strengthen torque outputted by therotating electrical machine. Specifically, the magnet unit includes thefirst magnets whose magnetization direction extends in an arc-shapetoward the center of the magnetic pole thereof and the second magnetswhose magnetization direction extends in an arc-shape toward the centerof the magnetic pole thereof. The first magnets are different inmagnetic polarity than the second magnets. The first magnets and thesecond magnets are arranged alternately in the circumferentialdirection. This enables the amount of magnetic flux in the magneticcircuit to be increased to enhance the torque produced by the rotatingelectrical machine. In this structure, most of the magnetic flux, asproduced by the magnet unit, passes through the magnet unit.Accordingly, in the seventieth disclosure, the first distance is set toa distance between the axial center of the rotor and the radially outersurface of the annular magnet unit in the radial direction.

The seventy-first disclosure relates to the structure, as set forth inany one of the sixty-fifth to the sixty-eighth disclosure, wherein therotor is arranged radially outside the stator. The magnet unit includesfirst magnets whose magnetization direction is oriented in the radialdirection and second magnets whose magnetization direction is orientedin a direction other than the radial direction. The first magnets arearranged at a given interval away from each other in the circumferentialdirection on a surface of the rotor which faces the stator. Each of thesecond magnets is disposed in the circumferentially adjacent firstmagnets. If an interval between magnetic poles of the magnet unit in thecircumferential direction is defined as df from the radially outersurface of the magnet unit, the first distance is a distance between aplace located away from a radially outer surface of the magnet unit bydf/2 outward in the radial direction and the axial center of the rotor,and the second distance is a distance between the axial center of therotor and a radially inner surface of the annular stator core in theradial direction.

The structure in the seventy-first disclosure is designed as an outerrotor structure. The second distance is, therefore, set to a distancebetween the axial center of the rotor and a radially inner surface ofthe annular stator core in the radial direction.

The structure in the seventy-first disclosure is equipped with the firstmagnets whose magnetization direction is oriented in the radialdirection and the second magnets whose magnetization direction isoriented in a direction other than the radial direction in order toincrease the amount of magnetic flux produced by the magnets. A portionof the magnetic flux produced by the magnet unit leaks from the statorcore. The magnetic circuit is, therefore, increased in size outward inthe radial direction, as compared with the ninth means. The effectsresulting from the increase in size in the outward radial direction maybe quantified as a function of the value df that is an interval betweenthe magnetic poles of the magnet unit in the circumferential direction.Accordingly, in the seventy-first disclosure, the first distance is setto a distance between the place located away from the radially outersurface of the magnet unit by df/2 outward in the radial direction andthe axial center of the rotor.

The seventy-second disclosure relates to the structure, as set forth inany one of the sixty-fifth to the sixty-eighth disclosure, wherein therotor is arranged radially inside the stator. The magnet unit includesthe first magnets whose magnetization direction extends in an arc-shapetoward the center of the magnetic pole thereof and the second magnetswhose magnetization direction extends in an arc-shape toward the centerof the magnetic pole thereof. The first magnets are different inmagnetic polarity than the second magnets. The first magnets and thesecond magnets are arranged on a surface of the rotor which faces thestator alternately in the circumferential direction. The first distanceis a distance between the axial center of the rotor and a radially outersurface of the annular stator core in the radial direction. The seconddistance is a distance between the axial center of the rotor and aradially inner surface of the magnet unit in the radial direction.

The structure in the seventy-second disclosure is designed as an innerrotor structure in which the rotor is arranged radially inside thestator. The second distance is, therefore, set to a distance between theaxial center of the rotor and a radially inner surface of the statorcore in the radial direction.

In the seventy-second disclosure, the polar anisotropic permanentmagnets are used. In this structure, most of the magnetic flux, asproduced by the magnet unit, passes through the magnet unit.Accordingly, in the seventy-second disclosure, the first distance is setto a distance between the axial center of the rotor and the radiallyouter surface of the stator core in the radial direction.

In the seventy-second disclosure, the rotor is arranged radially insidethe stator. The magnet unit includes the first magnets whosemagnetization direction is oriented in the radial direction and thesecond magnets whose magnetization direction is oriented in a directionother than the radial direction. Each of the second magnets is disposedbetween the circumferentially adjacent first magnets. If an intervalbetween magnetic poles of the magnet unit in the circumferentialdirection is defined as df from the radially outer surface of magnetunit, the first distance is a distance between a place located away froma radially inner surface of the stator core by df/2 inward in the radialdirection and the axial center of the rotor, and the second distance isa distance between the axial center of the rotor and a radially innersurface of the magnet unit in the radial direction.

The structure in the seventy-second disclosure is designed as an innerrotor structure in which the rotor is arranged radially inside thestator. The second distance is, therefore, set to a distance between theaxial center of the rotor and a radially inner surface of the statorcore in the radial direction.

The structure in the seventy-second disclosure is equipped with thefirst magnets whose magnetization direction is oriented in the radialdirection and the second magnets whose magnetization direction isoriented in a direction other than the radial direction in order toincrease the amount of magnetic flux produced by the magnets. In thisstructure, a portion of the magnetic flux produced by the magnet unitleaks from the stator core. Accordingly, in the seventy-seconddisclosure, the first distance is set to a distance between the placelocated away from the radially inner surface of the stator core by df/2inward in the radial direction and the axial center of the rotor in theradial direction.

The seventy-third disclosure relates to the structure, as set forth inany one of the sixty-ninth to the seventy-second disclosure, wherein thestator core has a thickness in the radial direction thereof which issmaller than that of the magnet unit in the radial direction and greaterthan that of the stator winding in the radial direction.

The structure in the seventy-third disclosure enables the stator toreceive magnetic flux generated by the magnets of the magnet unitwithout magnetic saturation and is capable of avoiding leakage ofmagnetic flux from the stator.

The seventy-fourth disclosure relates to the structure, as set forth inany one of the sixty-third to the seventy-third disclosure, wherein thestator winding is made using a conductor having a flattened crosssection whose thickness in a radial direction of the stator winding issmaller than a width thereof in a circumferential direction of thestator winding.

In the seventy-fourth disclosure, the conductor of the stator winding isdesigned in a flattened shape to have a thickness of the magnet facingportions decreased in the radial direction, thereby enabling the centersof the magnet facing portions in the radial direction to be arrangedclose to the magnet unit of the rotor. This minimizes the magneticsaturation occurring in the stator using the slot-less structure andincreases the density of magnetic flux in the magnetic facing portionsof the stator winding to increase the torque output.

The seventy-fifth disclosure relates to the structure, as set forth inany one of the sixty-third to the seventy-fourth disclosure, wherein ifa length of a portion of the magnetic unit equivalent to one magneticpole in the circumferential direction is defined as Cs, 2×DM/Cs isselected to be in a range of 3.5 or more and 12 or less.

The circumferential dimension of a surface of the magnet unit whichfaces the stator is approximately expressed by 2π×DM. The value of2π×DM/Cs indicates a ratio of a circumferential dimension of onemagnetic pole to the above circumferential dimension. When the value of2×DM/Cs is selected to be greater than or equal to 3.5 and smaller thanor equal to 12, an integer value of 2×DM/Cs will be 11 or more and 37 orless. Therefore, the number of magnetic poles in the above type of therotating electrical machine is a relatively great value, that is, in arange of 12 or more and 36 or less. This enables the amount of magneticflux produced by one magnetic pole to be decreased, thereby enabling thevolume of the magnets to be decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

The above described object, another object, features, or beneficialadvantages in this disclosure will be apparent from the appendeddrawings or the following detailed discussion.

In the drawings:

FIG. 1 is a perspective longitudinal sectional view of a rotatingelectrical machine.

FIG. 2 is a longitudinal sectional view of a rotating electricalmachine.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2 .

FIG. 4 is a partially enlarged sectional view of FIG. 3 .

FIG. 5 is an exploded view of a rotating electrical machine.

FIG. 6 is an exploded view of an inverter unit.

FIG. 7 is a torque diagrammatic view which demonstrates a relationshipbetween an ampere-turn and a torque density in a stator winding.

FIG. 8 is a transverse sectional view of a rotor and a stator.

FIG. 9 is an enlarged view of part of FIG. 8 .

FIG. 10 is a transverse sectional view of a stator.

FIG. 11 is a longitudinal sectional view of a stator.

FIG. 12 is a perspective view of a stator winding.

FIG. 13 is a perspective view of a conductor.

FIG. 14 is a schematic view illustrating a structure of a wire.

FIG. 15 is a schematic view which illustrates a cross section of a wire.

FIG. 16 is a schematic view which illustrates boron-containingmicrofiber.

FIG. 17 is a schematic view of a wire group containing CNT fiber.

FIG. 18(a) is a view for explaining an effect of decreasing eddy currentin a conventional structure.

FIG. 18(b) is a view for explaining an effect of decreasing eddy currentin the first embodiment.

FIG. 19(a) is a view for explaining an effect of decreasing eddycurrent.

FIG. 19(b) is a developed view of FIG. 19(a).

FIG. 20 is a view which illustrates a relation between a winding ratioand a thickness of a conductor.

FIG. 21 is a view for explaining electrical anisotropy in wire.

FIG. 22 is a view showing the layout of conductors at the n^(th) layerposition.

FIG. 23 is a side view showing conductors at the n^(th) layer positionand the (n+1)^(th) layer position.

FIG. 24 is a view representing a relation between an electrical angleand a magnetic flux density in magnets of an embodiment.

FIG. 25 is a view which represents a relation between an electricalangle and a magnetic flux density in a comparative example of magnets.

FIG. 26 is an electrical circuit diagram of a control system for arotating electrical machine.

FIG. 27 is a functional block diagram which shows a current feedbackcontrol operation of a control device.

FIG. 28 is a functional block diagram which shows a torque feedbackcontrol operation of a control device.

FIG. 29(a) is a time chart which represents an electrical currentflowing through a stator winding.

FIG. 29(b) is a time chart which represents and a change in torqueproduced by a rotating electrical machine.

FIG. 30 is a longitudinal sectional view of a rotating electricalmachine in a modified form of the first embodiment.

FIG. 31 is a longitudinal sectional view of a rotating electricalmachine in a modified form of the first embodiment.

FIG. 32 is a longitudinal sectional view of a rotating electricalmachine in a modified form of the first embodiment.

FIG. 33 is a longitudinal sectional view of bearings in a modified formof the first embodiment.

FIG. 34 is a transverse sectional view of a rotor and a stator in thesecond embodiment.

FIG. 35 is a partially enlarged view of FIG. 34 .

FIG. 36(a) is a view demonstrating flows of magnetic flux in aconventional magnet unit.

FIG. 36(b) is a view which illustrates a magnet unit equipped withmagnetic member in the second embodiment.

FIG. 37 is a view which represents a relation between an electricalangle and a magnetic flux density in magnets.

FIG. 38 is a view which illustrates a magnet unit in a modification ofthe second embodiment.

FIG. 39 is a view which illustrates a magnet unit in a modification ofthe second embodiment.

FIG. 40 is a view which represents a relation between a circumferentialangle and generated magnetic flux in second magnets.

FIG. 41 is a view for explaining definition of τ(=Ds/Ps).

FIG. 42 is a view which represents a relation between an electricalcurrent density and a value of τ.

FIG. 43 is a view which represents a relation among an electricalcurrent density, the number of poles, and a value of τ.

FIG. 44 is a perspective view which shows a stator winding in amodification 1 of the third embodiment.

FIG. 45 is a schematic view which illustrates joints of straightsections and turns.

FIG. 46 is a schematic view which illustrates joints of straightsections and turns in modification 2 of the third embodiment.

FIG. 47 is a longitudinal sectional view of a rotating electricalmachine in a modification 3 of the third embodiment.

FIG. 48 is a view which illustrates securement of turns in anothermodification of the third embodiment.

FIG. 49 is a view which partially illustrates straight sections andturns in another modification of the third embodiment.

FIG. 50 is a view which illustrates a structure of a rotor in anothermodification of the third embodiment.

FIG. 51 is a view which illustrates structures of a rotor and a statorin another modification of the third embodiment.

FIG. 52 is a view which illustrates a structure of a rotor in anothermodification of the third embodiment.

FIG. 53 is a view which illustrates a structure of a rotor in anothermodification of the third embodiment.

FIG. 54 is a view which illustrates a region near a stator winding inanother modification of the third embodiment.

FIG. 55 is a view which illustrates a region near a stator winding inanother modification of the third embodiment.

FIG. 56 is a longitudinal sectional view of a rotating electricalmachine in the fourth embodiment.

FIG. 57 is a longitudinal sectional view of a rotating electricalmachine in a modification 1 of the fourth embodiment.

FIG. 58 is a longitudinal sectional view of a rotating electricalmachine in a modification 2 of the fourth embodiment.

FIG. 59 is a view which illustrates a stator winding.

FIG. 60 is a longitudinal sectional view of a rotating electricalmachine in a modification 3 of the fourth embodiment.

FIG. 61 is a sectional view of a stator in the fifth embodiment.

FIG. 62 is a longitudinal sectional view of a stator in a modification 2of the fifth embodiment.

FIG. 63 is a sectional view of a stator in a modification 3 of the fifthembodiment.

FIG. 64 is a sectional view of a stator in a modification 4 of the fifthembodiment.

FIG. 65 is a partially enlarged longitudinal sectional view of arotating electrical machine in the sixth embodiment.

FIG. 66 is a partially enlarged transverse sectional view of a rotor anda stator.

FIG. 67 is a view which indicates the definition of df.

FIG. 68 is an enlarged transverse sectional view of a rotor and a statorin a modification 2 of the sixth embodiment.

FIG. 69 is a longitudinal sectional view of a rotating electricalmachine in a modification 3 of the sixth embodiment.

FIG. 70 is a longitudinal sectional view of a rotating electricalmachine in a modification 4 of the sixth embodiment.

FIG. 71 is a longitudinal sectional view of a rotating electricalmachine in a modification 5 of the sixth embodiment.

FIG. 72 is an explanatory view of a rotating electrical machine.

FIG. 73 is a view which illustrates a relation among reluctance torque,magnet torque, and distance DM.

FIG. 74 is a view which illustrates teeth.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The rotating electrical machine in the embodiments is configured to beused, for example, as a power source for vehicles. The rotatingelectrical machine may, however, be used widely for industrial,automotive, domestic, office automation, or game applications. In thefollowing embodiments, the same or equivalent parts will be denoted bythe same reference numbers in the drawings, and explanation thereof indetail will be omitted.

First Embodiment

The rotating electrical machine 10 in this embodiment is a synchronouspolyphase ac motor having an outer rotor structure (i.e., an outerrotating structure). The outline of the rotating electrical machine 10is illustrated in FIGS. 1 to 5 . FIG. 1 is a perspective longitudinalsectional view of the rotating electrical machine 10. FIG. 2 is alongitudinal sectional view along the rotating shaft 11 of the rotatingelectrical machine 10. FIG. 3 is a transverse sectional view (i.e.,sectional view taken along the line III-III in FIG. 2 ) of the rotatingelectrical machine 10 perpendicular to the rotating shaft 11. FIG. 4 isa partially enlarged sectional view of FIG. 3 . FIG. 5 is an explodedview of the rotating electrical machine 10. FIG. 3 omits hatchingshowing a section except the rotating shaft 11 for the sake ofsimplicity of the drawings. In the following discussion, a lengthwisedirection of the rotating shaft 11 will also be referred to as an axialdirection. A radial direction from the center of the rotating shaft 11will be simply referred to as a radial direction. A direction along acircumference of the rotating shaft 11 about the center thereof will besimply referred to as a circumferential direction.

The rotating electrical machine 10 includes the bearing unit 20, thehousing 30, the rotor 40, the stator 50, and the inverter unit 60. Thesemembers are arranged coaxially with each other together with therotating shaft 11 and assembled in a given sequence to complete therotating electrical machine 10.

The bearing unit 20 includes two bearings 21 and 22 arranged away fromeach other in the axial direction and the retainer 23 which retains thebearings 21 and 22. The bearings 21 and 22 are implemented by, forexample, radial ball bearings each of which includes the outer race 25,the inner race 26, and a plurality of balls 27 disposed between theouter race 25 and the inner race 26. The retainer 23 is of a cylindricalshape. The bearings 21 and 22 are disposed radially inside the retainer23. The rotating shaft 11 and the rotor 40 are retained radially insidethe bearings 21 and 22 to be rotatable.

The housing 30 includes the cylindrical peripheral wall 31. Theperipheral wall 31 has a first end and a second end opposed to eachother in an axial direction thereof. The peripheral wall 31 has the endsurface 32 on the first end and the opening 33 in the second end. Theopening 33 occupies the entire area of the second end. The end surface32 has formed in the center thereof the circular hole 34. The bearingunit 20 is inserted into the hole 34 and fixed using a fastener, such asa screw or a rivet. The hollow cylindrical rotor 40 and the hollowcylindrical stator 50 are disposed in an inner space defined by theperipheral wall 31 and the end surface 32 within the housing 30. In thisembodiment, the rotating electrical machine 10 is of an outer rotortype, so that the stator 50 is arranged radially inside the cylindricalrotor 40 within the housing 30. The rotor 40 is retained in a cantileverform by a portion of the rotating shaft 11 close to the end surface 32in the axial direction.

The rotor 40 includes the hollow cylindrical magnetic holder 41 and theannular magnet unit 42 disposed radially inside the magnet holder 41.The magnet holder 41 is of substantially a cup-shape and works as amagnet holding member. The magnet holder 41 includes the magnet retainer43, the fixing portion 44 which is of a cylindrical shape and smaller indiameter than the magnet retainer 43, and the intermediate portion 45connecting the magnet retainer 43 and the fixing portion 44 together.The magnet retainer 43 has the magnet unit 42 secured to an innerperipheral surface thereof.

The rotating shaft 11 passes through the through-hole 44 a of the fixingportion 44. The fixing portion 44 is secured to a portion of therotating shaft 11 disposed inside the through-hole 44 a. In other words,the magnet holder 41 is secured to the rotating shaft 11 through thefixing portion 44. The fixing portion 44 may preferably be joined to therotating shaft 11 using concavities and convexities, such as a splinejoint or a key joint, welding, or crimping, so that the rotor 40 rotatesalong with the rotating shaft 11.

The bearings 21 and 22 of the bearing unit 20 are secured radiallyoutside the fixing portion 44. The bearing unit 20 is, as describedabove, fixed on the end surface 32 of the housing 30, so that therotating shaft 11 and the rotor 40 are retained by the housing 30 to berotatable. The rotor 40 is, thus, rotatable within the housing 30.

The rotor 40 is equipped with the fixing portion 44 arranged only one ofends thereof opposed to each other in the axial direction of the rotor40. This cantilevers the rotor 40 on the rotating shaft 11. The fixingportion 44 of the rotor 40 is rotatably retained at two points ofsupports using the bearings 21 and 22 of the bearing unit 20 which arelocated away from each other in the axial direction. In other words, therotor 40 is held to be rotatable using the two bearings 21 and 22 whichare separate at a distance away from each other in the axial directionon one of the axially opposed ends of the magnet holder 41. This ensuresthe stability in rotation of the rotor 40 even though the rotor 40 iscantilevered on the rotating shaft 11. The rotor 40 is retained by thebearings 21 and 22 at locations which are away from the centerintermediate between the axially opposed ends of the rotor 40 in theaxial direction thereof.

The bearing 22 of the bearing unit 20 which is located closer to thecenter of the rotor 40 (a lower one of the bearings 21 and 22 in thedrawings) is different in dimension of a gap between each of the outerrace 25 and the inner race and the balls 27 from the bearing 21 which islocated farther away from the center of the rotor 40 (i.e., an upper oneof the bearings 21 and 22). For instance, the bearing 22 closer to thecenter of the rotor 40 is greater in the dimension of the gap from thebearing 21. This minimizes adverse effects on the bearing unit 20 whicharise from deflection of the rotor 40 or mechanical vibration of therotor 40 due to imbalance resulting from parts tolerance at a locationclose to the center of the rotor 40. Specifically, the bearing 22 closerto the center of the rotor 40 is engineered to have dimensions of thegaps or plays increased using precompression, thereby absorbing thevibration generated in the cantilever structure. The precompression maybe provided by either fixed position preload or constant pressurepreload. In the case of the fixed position preload, the outer race 25 ofeach of the bearings 21 and 22 is joined to the retainer 23 usingpress-fitting or welding. The inner race 26 of each of the bearings 21and 22 is joined to the rotating shaft 11 by press-fitting or welding.The precompression may be created by placing the outer race 25 of thebearing 21 away from the inner race 26 of the bearing 21 in the axialdirection or alternatively placing the outer race 25 of the bearing 22away from the inner race 26 of the bearing 22 in the axial direction.

The intermediate portion 45 includes a radially center portion and aradially outer portion and has a difference in level between theradially center portion and the radially outer portion in the axialdirection. In other words, the radially center portion and the radiallyouter portion are different in level from each other in the axialdirection. This layout results in a partial overlap between the magnetretainer 43 and the fixing portion 44 in the axial direction. In otherwords, the magnet retainer 43 protrudes outside a base end portion(i.e., a lower portion, as viewed in the drawing) of the fixing portion44 in the axial direction. The structure in this embodiment enables therotor 40 to be retained by the rotating shaft 11 at a location closer tothe center of gravity of the rotor 40 than a case where the intermediateportion 45 is shaped to be flat without any shoulder, thereby ensuringthe stability in operation of the rotor 40.

In the above described structure of the intermediate portion 45, therotor 40 has the annular bearing housing recess 46 which is formed in aninner portion of the intermediate portion 45 and radially surrounds thefixing portion 44. The bearing housing recess 46 has a portion of thebearing unit 20 disposed therein. The rotor 40 also has the coil housingrecess 47 which is formed in an outer portion of the intermediateportion 45 and radially surrounds the bearing housing recess 46. Thecoil housing recess 47 has disposed therein the coil end 54 of thestator winding 51 of the stator 50, which will be described later indetail. The housing recesses 46 and 47 are arranged adjacent each otherin the axial direction. In other words, a portion of the bearing unit 20is laid to overlap the coil end 54 of the stator winding 51 in the axialdirection. This enables the rotating electrical machine 10 to have alength decreased in the axial direction.

The coil end 54 may be bent radially inwardly or outwardly to have adecreased axial dimension, thereby enabling the axial length of thestator 50 to be decreased. A direction in which the coil end 54 is bentis preferably determined depending upon installation thereof in rotor40. In the case where the stator 50 is installed radially inside therotor 40, a portion of the coil end 54 which is inserted into the rotor40 is preferably bent radially inwardly. A coil end opposite the coilend 54 may be bent either inwardly or outwardly, but is preferably bentto an outward side where there is an enough space in terms of theproduction thereof.

The magnet unit 42 working as a magnetic portion is made up of aplurality of permanent magnets which are disposed radially inside themagnet retainer 43 to have different magnetic poles arranged alternatelyin a circumferential direction thereof. The magnet unit 42 will also bedescribed later in detail.

The stator 50 is arranged radially inside the rotor 40. The stator 50includes the stator winding 51 wound in a substantially cylindrical formand the stator core 52 arranged radially inside the stator winding 51.The stator winding 51 is arranged to face the annular magnet unit 42through a given air gap therebetween. The stator winding 51 includes aplurality of phase windings each of which is made of a plurality ofconductors which are arranged at a given pitch away from each other inthe circumferential direction and joined together. In this embodiment,two three-phase windings: one including a U-phase winding, a V-phasewinding, and a W-phase winging and the other including an X-phasewinding, a Y-phase winding, and a Z-phase winding are used to completethe stator winding 51 as a six-phase winding.

The stator core 52 is formed by an annular stack of magnetic steelplates made of soft magnetic material and mounted radially inside thestator winding 51.

The stator winding 51 overlaps the stator core 52 in the radialdirection and includes the coil side portion 53 disposed radiallyoutside the stator core 52 and the coil ends 54 and 55 overhanging atends of the stator core 52 in the axial direction. The coil side portion53 faces the stator core 52 and the magnet unit 42 of the rotor 40 inthe radial direction. The stator 50 is arranged inside the rotor 40. Thecoil end 54 that is one (i.e., an upper one, as viewed in the drawings)of the axially opposed coil ends 54 and 55 and arranged close to thebearing unit 20 is disposed in the coil housing recess 47 defined by themagnet holder 41 of the rotor 40. The stator 50 will also be describedlater in detail.

The inverter unit 60 includes the unit base 61 secured to the housing 30using fasteners, such as bolts, and a plurality of electrical components62 mounted on the unit base 61. The unit base 61 is made from, forexample, carbon fiber reinforced plastic (CFRP). The unit base 61includes the end plate 63 secured to an edge of the opening 33 of thehousing 30 and the casing 64 which is formed integrally with the endplate 63 and extends in the axial direction. The end plate 63 has thecircular opening 65 formed in the center thereof. The casing 64 extendsupward from a peripheral edge of the opening 65.

The stator 50 is arranged on an outer peripheral surface of the casing64. Specifically, an outer diameter of the casing 64 is selected to beidentical with or slightly smaller than an inner diameter of the statorcore 52. The stator core 52 is attached to the outer side of the casing64 to complete a unit made up of the stator 50 and the unit base 61. Theunit base 61 is secured to the housing 30, so that the stator 50 isunified with the housing 50 in a condition where the stator core 52 isinstalled on the casing 64.

The casing 64 has a radially inner storage space in which the electricalcomponents 62 are disposed. The electrical components 62 are arranged tosurround the rotating shaft 11 within the storage space. The casing 64functions as a storage space forming portion. The electrical components62 include the semiconductor modules 66, the control board 67, and thecapacitor module 68 which constitute an inverter circuit.

The inverter unit 60 will be also be described using FIG. 6 that is anexploded view in addition to FIGS. 1 to 5 .

The casing 64 of the unit base 61 includes the cylinder 71 and the endsurface 72 that is one of ends of the cylinder 71 which are opposed toeach other in the axial direction of the cylinder 71 (i.e., the end ofthe casing 64 close to the bearing unit 20). The end of the cylinder 71opposed to the end surface 72 in the axial direction is shaped to befully open through the opening 65 of the end plate 63. The end surface72 has formed in the center thereof the circular hole 73 through whichthe rotating shaft 11 is insertable.

The cylinder 71 of the casing 64 serves as a partition which isolatesthe rotor 40 and the stator 50 arranged radially outside the cylinder 71from the electrical components 62 arranged radially inside the cylinder71. The rotor 40, the stator 50, and the electrical components 62 arearranged radially inside and outside the cylinder 71.

The electrical components 62 are electrical devices making up theinverter circuit equipped with a motor function and a generatorfunction. The motor function is to deliver electrical current to thephase windings of the stator winding 51 in a given sequence to turn therotor 40. The generator function is to receive a three-phase ac currentflowing through the stator winding 51 in response to the rotation of therotating shaft 11 and generate and output electrical power. Theelectrical components 62 may be engineered to perform either one of themotor function and the generator function. In a case where the rotatingelectrical machine 10 is used as a power source for a vehicle, thegenerator function has a regenerative function to output a regeneratedelectrical power.

Specifically, the electrical components 62 include the hollowcylindrical capacitor module 68 arranged around the rotating shaft 11and the semiconductor modules 66 mounted on the capacitor module 68. Thecapacitor module 68 has a plurality of smoothing capacitors 68 aconnected in parallel to each other. Specifically, each of thecapacitors 68 a is implemented by a stacked-film capacitor which is madeof a plurality of film capacitors stacked in a trapezoidal shape incross section. The capacitor module 68 is made of the twelve capacitors68 a arranged in an annular shape.

The capacitors 68 a may be produced by preparing a long film which has agiven width and is made of a stack of films and cutting the long filminto isosceles trapezoids each of which has a height identical with thewidth of the long film and whose short bases and long bases arealternately arranged. Electrodes are attached to the thus producedcapacitor devices to complete the capacitors 68 a.

The semiconductor module 66 includes, for example, a semiconductorswitch, such as a MOSFET or an IGBT and is of substantially a planarshape. In this embodiment, the rotating electrical machine 10 is, asdescribed above, equipped with two sets of three-phase windings and hasthe inverter circuits, one for each set of the three-phase windings. Theelectrical components 62, therefore, include a total of twelvesemiconductor modules 66 which are arranged in an annular form to makeup the semiconductor module group 66A.

The semiconductor modules 66 are interposed between the cylinder 71 ofthe casing 64 and the capacitor module 68. The semiconductor modulegroup 66A has an outer peripheral surface placed in contact with aninner peripheral surface of the cylinder 71. The semiconductor modulegroup 66A also has an inner peripheral surface placed in contact with anouter peripheral surface of the capacitor module 68. This causes heat,as generated in the semiconductor modules 66, to be transferred to theend plate 63 through the casing 64, so that it is dissipated from theend plate 63.

The semiconductor modules 66 preferably has the spacers 69 disposedradially outside the outer peripheral surface thereof, i.e., between thesemiconductor modules 66 and the cylinder 71. A combination of thecapacitor modules 68 is so arranged as to have a regular dodecagonalsection extending perpendicular to the axial direction thereof, whilethe inner periphery of the cylinder 71 has a circular transversesection. The spacers 69 are, therefore, each shaped to have a flat innerperipheral surface and a curved outer peripheral surface. The spacers 69may alternatively be formed integrally with each other in an annularshape and disposed radially outside the semiconductor module group 66A.The spacers 69 are highly thermally conductive and made of, for example,metal, such as aluminum or heat dissipating gel sheet. The innerperiphery of the cylinder 71 may alternatively be shaped to have adodecagonal transverse section like the capacitor modules 68. In thiscase, the spacers 69 are each preferably shaped to have a flat innerperipheral surface and a flat outer peripheral surface.

In this embodiment, the cylinder 71 of the casing 64 has formed thereinthe coolant path 74 as a cooling portion through which coolant flows.The heat generated in the semiconductor modules 66 is also released tothe coolant flowing in the coolant path 74. In other words, the casing64 is equipped with a cooling mechanism. The coolant path 74 is, asclearly illustrated in FIGS. 3 and 4 , formed in an annular shape andsurrounds the electrical components 62 (i.e., the semiconductor modules66 and the capacitor module 68). The semiconductor modules 66 arearranged along the inner peripheral surface of the cylinder 71. Thecoolant path 74 is laid to overlap the semiconductor modules 66 in theradial direction.

The stator 50 is arranged outside the cylinder 71. The electricalcomponents 62 are arranged inside the cylinder 71. This layout causesthe heat to be transferred from the stator 50 to the outer side of thecylinder 71 and also transferred from the semiconductor modules 66 tothe inner side of the cylinder 71. It is possible to simultaneously coolthe stator 50 and the semiconductor modules 66, thereby facilitatingdissipation of thermal energy generated by heat-generating members ofthe rotating electrical machine 10.

The electrical components 62 include the insulating sheet 75 disposed onone of axially opposed end surfaces of the capacitor module 68 and thewiring module 76 disposed on the other end surface of the capacitormodule 68. The capacitor module 68 has two axially-opposed end surfaces:a first end surface and a second end surface. The first end surface ofthe capacitor module 68 closer to the bearing unit 20 faces the endsurface 72 of the casing 64 and is laid on the end surface 72 throughthe insulating sheet 75. The second end surface of the capacitor module68 closer to the opening 65 has the wiring module 76 mounted thereon.

The wiring module 76 includes the resin-made circular plate-shaped body76 a and a plurality of bus bars 76 b and 76 c embedded in the body 76a. The bus bars 76 b and 76 c electrically connect the semiconductormodules 66 and the capacitor module 68 together. Specifically, thesemiconductor modules 66 are equipped with the connecting pins 66 aextending from axial ends thereof. The connecting pins 66 a connect withthe bus bars 76 b radially outside the body 76 a. The bus bars 76 cextend away from the capacitor module 68 radially outside the body 76 aand have top ends connecting with the wiring members 79 (see FIG. 2 ).

The capacitor module 68, as described above, has the insulating sheet 75mounted on the first end surface thereof. The capacitor module 68,therefore, has two heat dissipating paths which extend from the firstand second end surfaces of the capacitor module 68 to the end surface 72and the cylinder 71. This enables the heat to be released from the endsurfaces of the capacitor module 68 other than the outer peripheralsurface on which the semiconductor modules 66 are arranged. In otherwords, it is possible to dissipate the heat not only in the radialdirection, but also in the axial direction.

The capacitor module 68 is of a hollow cylindrical shape and has therotating shaft 11 arranged therewithin at a given interval away from theinner periphery of the capacitor module 68, so that heat generated bythe capacitor module 68 will be dissipated from a hollow portion of thecapacitor module 68. The rotation of the rotating shaft 11 usuallyproduces a flow of air, thereby enhancing cooling effects.

The wiring module 76 has the disc-shaped control board 67 attachedthereto. The control board 67 includes a printed circuit board (PCB) onwhich given wiring patterns are formed and also has ICs and the controldevice 77 mounted thereon. The control device 77 serves as a controllerand is made of a microcomputer. The control board 67 is secured to thewiring module 76 using fasteners, such as screws. The control board 67has formed in the center thereof the hole 67 a through which therotating shaft 11 passes.

The control board 67 is disposed on one of the axial ends of the wiringmodule 76 which is on the opposite side to the capacitor module 68. Thebus bars 76 c of the wiring module 76 extend from one of surfaces of thecontrol board 67 to the other. The control board 67 may have cut-outsfor avoiding physical interference with the bus bars 76 c. For instance,the control board 67 may have the cut-outs formed in portions of thecircular outer edge thereof.

The electrical components 62 are, as described already, arranged insidethe space surrounded by the casing 64. The housing 30, the rotor 40, andthe stator 50 are disposed outside the space in the form of layers. Thisstructure serves to shield against electromagnetic noise generated inthe inverter circuits. Specifically, the inverter circuit works tocontrol switching operations of the semiconductor modules 66 in a PWMcontrol mode using a given carrier frequency. The switching operationsusually generate electromagnetic noise against which the housing 30, therotor 40, and the stator 50 which are arranged outside the electricalcomponents 62 shield.

The cylinder 71 has the through-holes 78 which are formed near the endplate 63 and through which the wiring members 79 (see FIG. 2 ) pass toelectrically connect the stator 50 disposed outside the cylinder 71 andthe electrical components 62 arranged inside the cylinder 71. The wiringmembers 79, as illustrated in FIG. 2 , connect with ends of the statorwinding 51 and the bus bars 76 c of the wiring module 76 using crimpingor welding techniques. The wiring members 79 are implemented by, forexample, bus bars whose joining surfaces are preferably flattened. Asingle through-hole 78 or a plurality of through-holes 78 are preferablyprovided. This embodiment has two through-holes 78. The use of the twothrough-holes 78 facilitates the ease with which terminals extendingfrom the two sets of the three-phase windings are connected by thewiring members 79, and is suitable for achieving multi-phase wireconnections.

The rotor 40 and the stator 50 are, as described already in FIG. 4 ,arranged within the housing 30 in this order in a radially inwarddirection. The inverter unit 60 is arranged radially inside the stator50. If a radius of the inner periphery of the housing 30 is defined asd, the rotor 40 and the stator 50 are located radially outside adistance of d×0.705 away from the center of rotation of the rotatingelectrical machine 10. If a region located radially inside the innerperipheral surface of the stator 50 (i.e., the inner circumferentialsurface of the stator core 52) is defined as a first region X1, and aregion radially extending from the inner peripheral surface of thestator 50 to the housing 30 is defined as a second region X2, an area ofa transverse section of the first region X1 is set greater than that ofthe second region X2. As viewed in a region where the magnet unit 42 ofthe rotor 40 overlaps the stator winding 51, the volume of the firstregion X1 is larger than that of the second region X2.

The rotor 40 and the stator 50 are fabricated as a magnetic circuitcomponent assembly. In the housing 30, the first region X1 which islocated radially inside the inner peripheral surface of the magneticcircuit component assembly is larger in volume than the region X2 whichlies between the inner peripheral surface of the magnetic circuitcomponent assembly and the housing 30 in the radial direction.

Next, the structures of the rotor 40 and the stator 50 will be describedbelow in more detail.

Typical rotating electrical machines are known which are equipped with astator with an annular stator core which is made of a stack of steelplates and has a stator winding wound in a plurality of slots arrangedin a circumferential direction of the stator core. Specifically, thestator core has teeth extending in a radial direction thereof at a giveninterval away from a yoke. Each slot is formed between the two radiallyadjacent teeth. In each slot, a plurality of conductors are arranged inthe radial direction in the form of layers to form the stator winding.

However, the above described stator structure has a risk that when thestator winding is energized, an increase in magnetomotive force in thestator winding may result in magnetic saturation in the teeth of thestator core, thereby restricting torque density in the rotatingelectrical machine. In other words, rotational flux, as created by theenergization of the stator winding of the stator core, is thought of asconcentrating on the teeth, which has a risk of causing magneticsaturation.

Generally, IPM (Interior Permanent Magnet) rotors are known which have astructure in which permanent magnets are arranged on a d-axis of a d-qaxis coordinate system, and a rotor core is placed on a q-axis of thed-q axis coordinate system. Excitation of a stator winding near thed-axis will cause an excited magnetic flux to flow from a stator to arotor according to Fleming's rules. This causes magnetic saturation tooccur widely in the rotor core on the q-axis.

FIG. 7 is a torque diagrammatic view which demonstrates a relationshipbetween an ampere-turn (AT) representing a magnetomotive force createdby the stator winding and a torque density (Nm/L). A broken lineindicates characteristics of a typical IPM rotor-rotating electricalmachine. FIG. 7 shows that in the typical rotating electrical machine,an increase in magnetomotive force in the stator will cause magneticsaturation to occur at two places: the tooth between the slots and theq-axis rotor (i.e., the rotor core on the q-axis), thereby restrictingan increase in torque. In this way, a design value of the ampere-turn isrestricted to be A1 or less in the typical rotating electrical machine.

In order to alleviate the above problem in this embodiment, the rotatingelectrical machine 10 is designed to have an additional structure, aswill be described below, in order to eliminate the restriction arisingfrom the magnetic saturation. Specifically, as a first measure, thestator 50 is designed to have a slot-less structure for eliminating themagnetic saturation occurring in the teeth of the stator core of thestator and also to use an SPM (Surface Permanent Magnet) rotor foreliminating the magnetic saturation occurring in a q-axis core of theIPM rotor. The first measure serves to eliminate the above described twoplaces where the magnetic saturation occurs, but however, may result ina decrease in torque in a low-current region (see an alternate long andshort dash line in FIG. 7 ). In order to alleviate this problem, as asecond measure, a polar anisotropic structure is employed to increase amagnetic path of magnets in the magnet unit 42 of the rotor 40 toenhance a magnetic force in order to increase a magnetic flux in the SPMrotor to minimize the torque decrease.

Additionally, as a third measure, a flattened conductor structure isemployed to decrease a thickness of conductors of the coil side portion53 of the stator winding 51 in the radial direction of the stator 50 forcompensating for the torque decrease. The above magnetic force-enhancedpolar anisotropic structure is thought of as resulting in a flow oflarge eddy current in the stator winding 51. The third measure is,however, to employ the flattened conductor structure in which theconductors have a decreased thickness in the radial direction, therebyminimizing the generation of the eddy current in the stator winding 51in the radial direction. In this way, the above first to thirdstructures are, as indicated by a solid line in FIG. 7 , expected togreatly improve the torque characteristics using strong magnetic forcemagnets and also alleviate a risk of generation of a large eddy currentresulting from the use of the high-magnetic force magnets.

Additionally, as a fourth measure, a magnet unit is employed which has apolar anisotropic structure to create a magnetic density distributionapproximating a sine wave. This increases a sine wave matchingpercentage using pulse control, as will be described later, to enhancethe torque and also results in a moderate change in magnetic flux,thereby minimizing an eddy-current loss.

As a fifth measure, the stator winding 51 is designed to have aconductor strand structure made of a bundle of wires. This causesfundamental wave components to be collected, thereby enabling a highcurrent or large amount of current to flow in the stator winding 51 andalso minimizing an eddy current occurring in the conductors widened inthe circumferential direction of the stator 50 more effectively than thethird measure in which the conductors are flattened in the radialdirection because each of the wires has a decreased transverse sectionalarea. The use of the bundle of the wires will cancel an eddy currentarising from magnetic flux occurring according to Ampere's circuital lawin response to the magnetomotive force produced by the conductors.

The use of the fourth and fifth measures minimizes the eddy-current lossresulting from the high magnetic force produced by the high-magneticforce magnets provided by the second measure and also enhance thetorque.

The slot-less structure of the stator 50, the flattened conductorstructure of the stator winding 51, and the polar anisotropic structureof the magnet unit 42 will be described below. The slot-less structureof the stator 50 and the flattened conductor structure of the statorwinding 51 will first be discussed. FIG. 8 is a transverse sectionalview illustrating the rotor 40 and the stator 50. FIG. 9 is a partiallyenlarged view illustrating the rotor 40 and the stator 50 in FIG. 8 .FIG. 10 is a transverse sectional view of the stator 50 taken along theline X-X in FIG. 11 . FIG. 11 is a longitudinal sectional view of thestator 50. FIG. 12 is a perspective view of the stator winding 51. FIGS.8 and 9 indicate directions of magnetization of magnets of the magnetunit 42 using arrows.

The stator core 52 is, as clearly illustrated in FIGS. 8 to 11 , of acylindrical shape and made of a plurality of magnetic steel platesstacked in the axial direction of the stator core 52 to have a giventhickness in a radial direction of the stator core 52. The statorwinding 51 is mounted on the outer periphery of the stator core 52 whichfaces the rotor 40. The outer peripheral surface of the stator core 52facing the rotor 40 serves as a conductor mounting portion (i.e., aconductor area). The outer peripheral surface of the stator core 52 isshaped as a curved surface without any irregularities. A plurality ofconductor groups 81 are arranged on the outer peripheral surface of thestator core 52 at given intervals away from each other in thecircumferential direction of the stator core 52. The stator core 52functions as a back yoke that is a portion of a magnetic circuit workingto rotate the rotor 40. The stator 50 is designed to have a structure inwhich a tooth (i.e., a core) made of a soft magnetic material is notdisposed between a respective two of the conductor groups 81 arrangedadjacent each other in the circumferential direction (i.e., theslot-less structure). In this embodiment, a resin material of thesealing member 57 is disposed in the space or gap 56 between arespective adjacent two of the conductor groups 81. Before the sealingmembers 57 are placed to seal the gaps 56, the conductor groups 81 arearranged in the circumferential direction radially outside the statorcore 52 at a given interval away from each other through the gaps 56that are conductor-to-conductor regions. This makes up the slot-lessstructure of the stator 50.

The structure, as referred to herein, in which the teeth arerespectively disposed between the conductor groups 81 arrayed in thecircumferential direction means that each of the teeth has a giventhickness in the radial direction and a given width in thecircumferential direction of the stator 50, so that a portion of themagnetic circuit, that is, a magnet magnetic path lies between theadjacent conductor groups 81. In contrast, the structure in which notooth lies between the adjacent conductor groups 81 means that there isno magnetic circuit between the adjacent conductor groups 81.

The stator winding 51 is, as can be seen in FIGS. 10 and 11 , sealed bythe sealing members 57 which are formed by a synthetic resin. As atransverse section is viewed in FIG. 10 , each of the sealing members 57is formed by placing synthetic resin between the conductor groups 81,that is, in the gap 56. In other words, the sealing member 57 providesan insulating member between the conductor groups 81. Each of thesealing members 57, therefore, functions as an insulator in acorresponding one of the gaps 56. The sealing members 57 occupy a regionwhich is located radially outside the stator core 52 and in which allthe conductor groups 81 are disposed, in other words, which is definedto have a dimension larger than that of each of the conductor groups 81in the radial direction.

As a longitudinal section is viewed in FIG. 11 , the sealing members 57lie to occupy a region including the turns 84 of the stator winding 51.Radially inside the stator winding 51, the sealing members 57 lie in aregion including at least a portion of the axially opposed ends of thestator core 52. In this case, the stator winding 51 is fully sealed bythe resin except for the ends of each phase winding, i.e., terminalsjoined to the inverter circuits.

The structure in which the sealing members 57 are disposed in the regionincluding the ends of the stator core 52 enables the sealing members 57to compress the stack of the steel plates of the stator core 52 inwardlyin the axial direction. In other words, the sealing members 57 work tofirmly retain the stack of the steel plates of the stator core 52. Inthis embodiment, the inner peripheral surface of the stator core 52 isnot sealed using resin, but however, the whole of the stator core 52including the inner peripheral surface may be sealed using resin.

In a case where the rotating electrical machine 10 is used as a powersource for a vehicle, the sealing members 57 are preferably made of ahigh heat-resistance fluororesin, epoxy resin, PPS resin, PEEK resin,LCP resin, silicon resin, PAI resin, or PI resin. In terms of a linearcoefficient expansion to minimize damage to the sealing members 57 dueto an expansion difference, the sealing members 57 are preferably madeof the same material as that of an outer film of the conductors of thestator winding 51. The silicon resin whose linear coefficient expansionis twice those of other resins is preferably excluded from the materialof the sealing members 57. In a case of electrical products, such aselectric vehicles equipped with no combustion engine, PPO resin, phenolresin, or FRP resin which resists 180° C. may be used, except in fieldswhere an ambient temperature of the rotating electrical machine isexpected to be lower than 100° C.

The degree of torque outputted by the rotating electrical machine 10 isusually proportional to the degree of magnetic flux. In a case where astator core is equipped with teeth, a maximum amount of magnetic flux inthe stator core is restricted depending upon the saturation magneticflux density in the teeth, while in a case where the stator core is notequipped with teeth, the maximum amount of magnetic flux in the statorcore is not restricted. Such a structure is, therefore, useful forincreasing an amount of electrical current delivered to the statorwinding 51 to increase the degree of torque produced by the rotatingelectrical machine 10.

Each of the conductor groups 81 arranged radially outside the statorcore 52 is made of a plurality of conductors 82 whose transverse sectionis of a flattened rectangular shape and which are disposed on oneanother in the radial direction of the stator core 52. Each of theconductors 82 is oriented to have a transverse section meeting arelation of dimension in radial direction<dimension in circumferentialdirection. This causes each of the conductor groups 81 to be thin in theradial direction. A conductive region of the conductor group 81 alsoextends inside a region occupied by teeth of a typical stator. Thiscreates a flattened conductive region structure in which a sectionalarea of each of the conductors 82 is increased in the circumferentialdirection, thereby alleviating a risk that the amount of thermal energymay be increased by a decrease in sectional area of a conductor arisingfrom flattening of the conductor. A structure in which a plurality ofconductors are arranged in the circumferential direction and connectedin parallel to each other is usually subjected to a decrease insectional area of the conductors by a thickness of a coated layer of theconductors, but however, has beneficial advantages obtained for the samereasons as described above.

The stator 50 in this embodiment is, as described already, designed tohave no slots, thereby enabling the stator winding 51 to be designed tohave a conductive region of an entire circumferential portion of thestator 50 which is larger in size than a non-conductive regionunoccupied by the stator winding 51 in the stator 50. In typicalrotating electrical machines for vehicles, a ratio of the conductiveregion/the non-conductive region is usually one or less. In contrast,this embodiment has the conductor groups 81 arranged to have theconductive region substantially identical in size with or larger in sizethan the non-conductive region. If the conductor region, as illustratedin FIG. 10 , occupied by the conductor 82 (i.e., the straight section 83which will be described later in detail) in the circumferentialdirection is defined as WA, and a conductor-to-conductor region that isan interval between a respective adjacent two of the conductors 82 isdefined as WB, the conductor region WA is larger in size than theconductor-to-conductor region WB in the circumferential direction.

The degree of torque produced by the rotating electrical machine 10 issubstantially inversely proportional to the thickness of the stator core52 in the radial direction. The conductor groups 81 arranged radiallyoutside the stator core 52 are, as described above, designed to have thethickness decreased in the radial direction. This design is useful inincreasing the degree of torque outputted by the rotating electricalmachine 10. This is because a distance between the magnet unit 42 of therotor 40 and the stator core 52 (i.e., a distance in which there is noiron) may be decreased to decrease the magnetic resistance. This enablesinterlinkage magnetic flux in the stator core 52 produced by thepermanent magnets to be increased to enhance the torque.

Each of the conductors 82 is made of a coated conductor formed bycovering the surface of the conductor body 82 a with the insulatingcoating 82 b. The conductors 82 stacked on one another in the radialdirection are, therefore, insulated from each other. Similarly, theconductors 82 are insulated from the stator core 52. The insulatingcoating 82 b of the conductor 82 has a thickness of, for example, 80 μmwhich is greater than that (e.g., 20 to 40 μm) of a coating of a typicalconductor. This ensures the insulation between the conductors 82 and thestator core 52 without use of insulating sheet therebetween. Each phasewinding made of the conductors 82 is insulated by the coating 82 bexcept an exposed portion thereof for joining purposes. The exposedportion includes, for example, an input or an output terminal or aneutral point in a case of a star connection. The conductor groups 81arranged adjacent each other in the radial direction are firmly adheredto each other using resin or self-bonding coated wire, therebyminimizing a risk of insulation breakdown, mechanical vibration, ornoise caused by rubbing of the conductors 82.

In this embodiment, the conductor body 82 a is made of a collection of aplurality of wires 86. The conductor body 82 a has the wires 86connected in parallel to each other. Specifically, the conductor body 82a is, as can be seen in FIG. 13 , made of a strand of the twisted wires86. The conductor body 82 a is equivalent to an anisotropic conductor.Usually, the electrical resistance of a wire is inversely proportionalto a sectional area thereof. Accordingly, the more the number of thewires 86, the smaller the sectional area of each of the wires 86,thereby resulting in greater attenuation of the eddy current. Each ofthe wires 86 is, as can be seen in FIG. 14 , made of a bundle of aplurality of thin conductive fibers 87. For instance, each of the wires86 may be made of a complex of CNT (carbon nanotube) fibers. The CNTfibers include boron-containing microfibers in which at least a portionof carbon is substituted with boron. Instead of CNT fibers that arecarbon-based microfibers, vapor grown carbon fiber (VGCF) may be used,but however, CNT fiber is preferable. The surface of the wire 86 is, asillustrated in FIG. 15 , covered with a layer of insulating polymer,such as enamel.

The conductor body 82 a is, as described above, made of the twistedwires 86, thereby reducing an eddy current created in each of the wires86, which reduces an eddy current in the conductor body 82 a. Each ofthe wires 86 is twisted, thereby causing each of the wires 86 to haveportions where directions of applied magnetic field are opposite eachother, which cancels a back electromotive force. This results in areduction in the eddy current. Particularly, each of the wires 86 ismade of the conductive fibers 87, thereby enabling the conductive fibers87 to be thin and also enabling the number of times the conductivefibers 87 are twisted to be increased, which enhances the reduction ineddy current.

The wires 86 made of a complex of CNT (Carbon Nanotube) fibers will bedescribed below. The electrical resistance of CNT is expected to belower than one-fifth of that of copper wire. This embodiment uses, asCNT fibers, boron-containing fine fibers in which at least a portion ofcarbon is replaced with boron. The boron-containing fine fibers usuallyhave high conductivity, thus enabling the conductors 82 to have agreatly decreased electrical resistance. Instead of CNT fibers, vaporgrown carbon fibers (VGCFs) may be used as carbon fine fibers, but CNTfibers are useful in this embodiment.

As CNT fibers, carbon fine fibers in which all atoms of carbon are, asillustrated in FIG. 16 , substituted with atoms of boron and nitrogenare preferably used. A ratio of boron and nitrogen in the boronnitrogen-containing fine fibers is preferably 1:1.

The boron nitrogen-containing fine fibers may be made by executing astep in which a fiber aggregate including carbon fine fibers is mixedwith atoms of boron and then heated in a nitrogen atmosphere to change aportion of the carbon fine fibers into boron nitrogen-containing finefibers or a step in which a fiber aggregate including carbon fine fibersis mixed with atoms of boron and then heated in an inert gas atmosphereto change a portion of the carbon fine fibers into boron-containing finefibers. The substitution of carbon in CNT may be made in a method taughtin Japanese Patent No. 4577385.

The above method will be discussed below. CNT wire and boron are inputin a heating graphite crucible to have a molar ratio of 2:1, heated forthirty minutes at 2,000° C. under an argon atmosphere (i.e., 200 sccm,1.0 atm) in a high-frequency heating furnace, and then naturally cooledto room temperature. In this step, at least a portion of carbon in aportion of CNT constituting the CNT wire is substituted with boron. Thegraphite crucible is ejected from the heating furnace. Boron is alsoadded to the graphite crucible so that the CNT wire and boron have amolar ratio of 5:1. The graphite crucible is then heated for thirtyminutes at 2,000° C. under a nitrogen atmosphere (200 sccm, 1.0 atm) inthe heating furnace. In this step, carbon is, as illustrated in FIG. 16, substituted with nitrogen and boron in a portion of CNT constitutingthe CNT wire. In the CNT in which carbon is substituted with boron andnitrogen, divalent electrons of nitrogen forming a six-membered ring hashigh electronegativity so that they cannot be moved freely. The CNT inwhich carbon is substituted with boron and nitrogen, therefore, haselectrical insulation properties. In the following discussion, wire inwhich carbon in a portion of CNT is substituted with boron and nitrogenwill also be referred to as treated CNT wire. CNT wire in which carbonis not substituted will also be referred to as untreated CNT wire. Thetreated CNT wire 222, as illustrated in FIG. 17(a), has an outer layercovered with the treated CNT 224 in which carbon is substituted withboron and nitrogen. The center of the treated CNT wire 222 includes amixture of CNT 223 in which carbon is not substituted with boron andnitrogen and CNT 225 in which carbon is partially substituted withboron.

The treated CNT wire may be as illustrated in FIG. 17(a), made of amixture of the CNT 223 in which carbon is not substituted with boron andnitrogen, the CNT 224 in which carbon is partially substituted withboron, and the CNT 223 in which carbon is not substituted with boron andnitrogen.

Generally, a stator winding is, as illustrated in FIG. 18(a), made of athick conductor (which has, for example, a rectangular section), so thata magnetic field H applied to the conductor develops a loop-shaped eddycurrent Ie1. The conductor has a high uniform electrical conductivity,so that there is no block for the eddy current, thereby resulting in anincreased area where the eddy current Ie1 flows in the loop shape, sothat the eddy current becomes great. In contrast, the conductor body 82a in this embodiment is, as illustrated in FIG. 18(b), made of aplurality of twisted wires 86 each of which is covered with aninsulating layer, so that no eddy current flows one of the wires 86 toanother, thus resulting in a decrease in area where the eddy current Ie1flows in the loop shape, so that the amount of the eddy current Ie1become small.

Each of the wires 86 is twisted, thereby causing each of the wires 86 tohave portions, as illustrated in FIG. 19(a), where directions of appliedmagnetic field are opposite each other, which cancels a backelectromotive force as viewed in FIG. 19(a) in which the wire 96 isdeveloped. This results in a reduction in the eddy current.Particularly, each of the wires 86 is made of the conductive fibers 87,thereby enabling the conductive fibers 87 to be thin and also enablingthe number of times the conductive fibers 87 are twisted to beincreased, which enhances the reduction in eddy current.

If a distance between a radially inner peripheral surface of the magnetunit 42 and a radially outer peripheral surface of the stator core 52is, as illustrated in FIG. 4 , defined as g1, and a distance between theradially inner peripheral surface of the magnet unit 42 and a radiallyouter peripheral surface of the stator winding 51 is defined as g2, thethickness of the stator winding 51 in the radial direction is given byg1−g2. In the following discussion, a winding ratio K is defined asK=(g1−g2)/g1. The use of the CNT fibers, as can be seen in FIG. 20 ,enables the winding ratio K to be 66% or less. FIG. 20 is a view whichrepresents a relation between the thickness of a conductor and thewinding ratio K. In FIG. 20 , a vertical axis expresses the windingratio K in percentage. The reason why the winding ratio K is decreasedis that the use of CNT results in a great increase in electricalconductivity to enhance a packaging density of electric loading. Thisresults in a great decrease in distance between the radially innerperipheral surface of the magnet unit 42 and the radially peripheralsurface of the stator core 52, thereby greatly decreasing the magneticresistance in the magnetic circuit. This enables magnetomotive forcerequired to generate equal amounts of magnetic flux to be decreased todecrease the thickness of the permanent magnets of the rotor.

FIG. 20 demonstrates a design example where the stator core 52 has anouter diameter of about 200 mm. In a case of use of copper wire, it isimpossible for a percentage of occupancy of a conductor in a void spaceto be lower than 75%. It is difficult to decrease the length of the voidspace. Usually, copper alloy is higher in electrical resistivity thanpure copper. It is impossible even for silver that is lower inelectrical resistance than pure copper to have the winding ratio K lessthan 70%. For example, it is possible to use a high-temperaturesuperconductor, but however, an existing operable temperature thereof isfar from room temperatures. It is, therefore, impossible to use ahigh-temperature superconductor especially with automobiles. Theresistance in CNT may be kept low even at room temperature. CNT is,thus, useful in decreasing the distance between the radially innerperipheral surface of the magnet unit 42 and the radially outerperipheral surface of the stator core 52.

Instead of the wires 86 fully covered with the polymer insulating later86 a, at least one of the wires 86 may be partially covered with thepolymer insulating layer 86 a.

In the case where the wires 86 have electrical anisotropy, it is notnecessary to cover all the wires 86 with the polymer insulating layer 86a. Such a characteristic is, as shown in FIG. 21 , that the electricalresistance Rb to flow of electrical current between the adjacent wires86 is greatly higher than the electrical resistance Ra of the wire 86 toflow of electrical current through itself. This blocks the eddy currentwithout use of insulating layers. It is, thus, possible to minimize heatgeneration at low cost.

Each of the wires 86 is, as described above, made of the conductivefibers 87, thereby enabling a current flow path in the conductors 82 tobe thinner, which also enables the number of times the current flow pathis twisted to be increased, thereby minimizing the eddy current. Thewires 86 may be made of a composite conductor containing copper andcarbon nanotube fibers.

The conductors 82 are, as described above, of a low-profile or flattenedrectangular shape in cross section and arranged in the radial direction.For example, each of the conductors 82 is made of a strand of the wires86 and twisted into a desired shape using synthetic resin.

The conductors 82 are each bent and arranged in a given pattern in thecircumferential direction of the stator winding 51, thereby forming thephase-windings of the stator winding 51. The stator winding 51, asillustrated in FIG. 12 , includes the coil side portion 53 and the coilends 54 and 55. The conductors 82 have the straight sections 83 whichextend straight in the axial direction of the stator winding 51 and formthe coil side portion 53. The conductors 82 have the turns 84 which arearranged outside the coil side portion 53 in the axial direction andform the coil ends 54 and 55. Each of the conductor 82 is made of awave-shaped string of conductor formed by alternately arranging thestraight sections 83 and the turns 84. The straight sections 83 arearranged to face the magnet unit 42 in the radial direction. Thestraight sections 83 are arranged at a given interval away from eachother and joined together using the turns 84 located outside the magnetunit 42 in the axial direction. The straight sections 83 correspond tomagnet facing portions.

In this embodiment, the stator winding 51 is shaped in the form of anannular distributed winding. In the coil side portion 53, the straightsections 83 are arranged at an interval away from each other whichcorresponds to each pole pair of the magnet unit 42 for each phase. Ineach of the coil ends 54 and 55, the straight sections 83 for each phaseare joined together by the turn 84 which is of a V-shape. The straightsections 83 which are paired for each pole pair are opposite to eachother in a direction of flow of electrical current. A respective two ofthe straight sections 83 which are joined together by each of the turns84 are different between the coil end 54 and the coil end 55. The jointsof the straight sections 83 by the turns 84 are arranged in thecircumferential direction on each of the coil ends 54 and 55 to completethe stator winding in a hollow cylindrical shape.

More specifically, the stator winding 51 is made up of two pairs of theconductors 82 for each phase. The stator winding 51 is equipped with afirst three-phase winding set including the U-phase winding, the V-phasewinding, and the W-phase winding and a second three-phase phase windingset including the X-phase winding, the Y-phase winding, and the Z-phasewinding. The first three-phase phase winding set and the secondthree-phase winding set are arranged adjacent each other in the radialdirection in the form of two layers. If the number of phases of thestator winding 51 is defined as S (i.e., 6 in this embodiment), thenumber of the conductors 82 for each phase is defined as m, then2×S×m=2Sm conductors 82 are used for each pole pair in the statorwinding 51. The rotating electrical machine in this embodiment isdesigned so that the number of phases S is 6, the number m is 4, and 8pole pairs are used. 6×4×8=192 conductors 82 are arranged in thecircumferential direction of the stator core 52.

The stator winding 51 in FIG. 12 is designed to have the coil sideportion 53 which has the straight sections 82 arranged in the form oftwo overlapping layers disposed adjacent each other in the radialdirection. Each of the coil ends 54 and 55 has a respective two of theturns 84 which extend from the radially overlapping straight sections 82in opposite circumferential directions. In other words, the conductors82 arranged adjacent each other in the radial direction are opposite toeach other in direction in which the turns 84 extend except for ends ofthe stator winding 51.

A winding structure of the conductors 82 of the stator winding 51 willbe described below in detail. In this embodiment, the conductors 82formed in the shape of a wave winding are arranged in the form of aplurality of layers (e.g., two layers) disposed adjacent or overlappingeach other in the radial direction. FIGS. 22(a) and 2(b) illustrate thelayout of the conductors 82 which form the n^(th) layer. FIG. 22(a)shows the configurations of the conductor 82, as viewed from the side ofthe stator winding 51. FIG. 22(b) shows the configurations of theconductors 82 as viewed in the axial direction of the stator winding 51.In FIGS. 22(a) and 22(b), locations of the conductor groups 81 areindicated by symbols D1, D2, D3 . . . , and D9. For the sake ofsimplicity of disclosure, FIGS. 22(a) and 2(b) show only threeconductors 82 which will be referred to herein as the first conductor82_A, the second conductor 82_B, and the third conductor 82_C.

The conductors 82_A to 82_C have the straight sections 83 arranged at alocation of the n^(th) layer, in other words, at the same position inthe circumferential direction. Every two of the straight sections 82which are arranged at 6 pitches (corresponding to 3×m pairs) away fromeach other are joined together by one of the turns 84. In other words,in the conductors 82_A to 82_C, an outermost two of the seven straightsections 83 arranged in the circumferential direction of the statorwinding 51 on the same circle defined about the center of the rotor 40are joined together using one of the turns 84. For instance, in thefirst conductor 82_A, the straight sections 83 placed at the locationsD1 and D7 are joined together by the inverse V-shaped turn 84. Theconductors 82_B and 82_C are arranged at an interval equivalent to aninterval between a respective adjacent two of the straight sections 83away from each other in the circumferential direction at the location ofthe n^(th) layer. In this layout, the conductors 82_A to 82_C are placedat a location of the same layer, thereby resulting in a risk that theturns 84 thereof may physically interfere with each other. In order toalleviate such a risk, each of the turns 84 of the conductors 82_A to82_C in this embodiment is shaped to have an interference avoidingportion formed by offsetting a portion of the turn 84 in the radialdirection.

Specifically, the turn 84 of each of the conductors 82_A to 82_Cincludes the slant portion 84 a, the head portion 84 b, the slantportion 84 c, and the return portion 84 d. The slant portion 84 aextends in the circumferential direction of the same circle (which willalso be referred to as a first circle). The head portion 84 extends fromthe slant portion 84 a radially inside the first circle (i.e., upward inFIG. 22(b)) to reach another circle (which will also be referred to as asecond circle). The slant portion 84 c extends in the circumferentialdirection of the second circle. The return portion 84 d returns from thesecond circle back to the first circle. The head portion 84 b, the slantportion 84 c, and the return portion 84 d define the interferenceavoiding portion. The slant portion 84 c may be arranged radiallyoutside the slant portion 84 a.

In other words, each of the conductors 82_A to 82_C has the turn 84shaped to have the slant portion 84 a and the slant portion 84 c whichare arranged on opposite sides of the head portion 84 b at the center inthe circumferential direction. The locations of the slant portions 84 aand 84 b are different from each other in the radial direction (i.e., adirection perpendicular to the drawing of FIG. 15(a) or a verticaldirection in FIG. 15(b)). For instance, the turn 84 of the firstconductor 82_A is shaped to extend from the location D1 on the n^(th)layer in the circumferential direction, be bent at the head portion 84 bthat is the center of the circumferential length of the turn 84 in theradial direction (e.g., radially inwardly), be bent again in thecircumferential direction, extend again in the circumferentialdirection, and then be bent at the return portion 84 d in the radialdirection (e.g., radially outwardly) to reach the location D9 on then^(th) layer.

With the above arrangements, the slant portions 84 a of the conductors82_A to 82_C are arranged vertically or downward in the order of thefirst conductor 82_A, the second conductor 82_B, and the third conductor82_C. The head portions 84 b change the order of the locations of theconductors 82_A to 82_C in the vertical direction, so that the slantportions 84 c are arranged vertically or downward in the order of thethird conductor 82_3, the second conductor 82_B, and the first conductor82_A. This layout achieves an arrangement of the conductors 82_A to 82_Cin the circumferential direction without any physical interference witheach other.

In the structure wherein the conductors 82 are laid to overlap eachother in the radial direction to form the conductor group 81, the turns84 leading to a radially innermost one and a radially outermost one ofthe straight sections 83 forming the two or more layers are preferablylocated radially outside the straight sections 83. In a case where theconductors 82 forming the two or more layers are bent in the same radialdirection near boundaries between ends of the turns 84 and the straightsections 83, the conductors 82 are preferably shaped not to deterioratethe insulation therebetween due to physical interference of theconductors 82 with each other.

In the example of FIGS. 22(a) and 22(b), the conductors 82 laid on eachother in the radial direction are bent radially at the return portions84 d of the turns 84 at the location D7 to D9. It is advisable that theconductor 82 of the n^(th) layer and the conductor 82 of the n+1^(th)layer be bent, as illustrated in FIG. 16 , at radii of curvaturedifferent from each other. Specifically, the radius of curvature R1 ofthe conductor 82 of the n^(th) layer is preferably selected to besmaller than the radius of curvature R2 of the conductor 82 of then+1^(th) layer.

Additionally, radial displacements of the conductor 82 of the n^(th)layer and the conductor 82 of the n+1^(th) layer are preferably selectedto be different from each other. If the amount of radial displacement ofthe conductor 82 of the n^(th) layer is defined as S1, and the amount ofradial displacement of the conductor 82 of the n+1^(th) layer locatedradially outside the nth layer defined as S2, the amount of radialdisplacement S1 is preferably selected to be greater than the amount ofradial displacement S2.

The above layout of the conductors 82 eliminates the risk ofinterference with each other, thereby ensuring a required degree ofinsulation between the conductors 82 even when the conductors 82 laid oneach other in the radial direction are bent in the same direction.

The structure of the magnet unit 42 of the rotor 40 will be describedbelow. In this embodiment, the magnet unit 42 is made of permanentmagnets in which a remanent flux density Br=1.0 T, and an intrinsiccoercive force Hcj=400 kA/m. 5,000 to 10,000 AT is applied to themagnets. The demagnetization of the magnets is, therefore, avoided bydesigning the magnets to have a length of 25 mm for paired magneticpoles. In this embodiment, permanent magnets are used which aremagnetically oriented to control the easy axis of magnetization thereof,thereby enabling a magnetic circuit length within the magnets to belonger than that within typical linearly oriented magnets which producesa magnetic flux density of 1.0 T or more. In other words, the magneticcircuit length for one pole pair in the magnets in this embodiment maybe achieved using the magnets with a small volume. Additionally, a rangeof reversible flux loss in the magnets is not lost when subjected tosevere high temperatures, as compared with use of typical linearlyoriented magnets. The inventors of this application have found thatcharacteristics similar to those of anisotropic magnets are obtainedeven using conventional magnets.

The magnet unit 42 is, as clearly illustrated in FIGS. 8 and 9 , of anannular shape and arranged inside the magnet holder 41 (specifically,radially inside the cylinder 43). The magnet unit 42 is equipped withthe first magnets 91 and the second magnets 92 which are each made of apolar anisotropic magnet. Each of the first magnets 91 and each of thesecond magnets 92 are different in polarity from each other. The firstmagnets 91 and the second magnets 92 are arranged alternately in thecircumferential direction of the magnet unit 42. Each of the firstmagnets 91 is engineered to have a portion creating an N-pole near thestator winding 51. Each of the second magnets 92 is engineered to have aportion creating an S-pole near the stator winding 51. The first magnets91 and the second magnets 92 are each made of, for example, a permanentrare earth magnet, such as a neodymium magnet.

Each of the magnets 91 and 92 is engineered to have a direction ofmagnetization which extends in an annular shape in between a d-axis anda q-axis where the d-axis represents the center of a magnetic pole, andthe q-axis represents a magnetic boundary between the magnetic poles. Inthe magnet unit 42, a magnetic flux flows in an annular shape between arespective adjacent two of the N-poles and the S-poles of the magnets 91and 92, so that each of the magnetic paths has an increased length, ascompared with, for example, radial anisotropic magnets. A distributionof the magnetic flux density will, therefore, exhibit a shape similar toa sine wave illustrated in FIG. 24 . This facilitates concentration ofmagnetic flux around the center of the magnetic pole unlike adistribution of magnetic flux density of a radial anisotropic magnetdemonstrated in FIG. 25 as a comparative example, thereby enabling thedegree of torque produced by the rotating electrical machine 10 to beincreased. It has also been found that the magnet unit 42 in thisembodiment has the distribution of the magnetic flux density distinctfrom that of a typical Halbach array magnet. In FIGS. 24 and 25 , ahorizontal axis indicates the electrical angle, while a vertical axisindicates the magnetic flux density. 90° on the horizontal axisrepresents the d-axis (i.e., the center of the magnetic pole). 0° and180° on the horizontal axis represent the q-axis.

The sine wave matching percentage in the distribution of the magneticflux density is preferably set to, for example, 40% or more. Thisimproves the amount of magnetic flux around the center of a waveform ofthe distribution of the magnetic flux density as compared with aradially oriented magnet or a parallel oriented magnet in which the sinewave matching percentage is approximately 30%. By setting the sine wavematching percentage to be 60% or more, the amount of magnetic fluxaround the center of the waveform is improved, as compared with aconcentrated magnetic flux array, such as the Halbach array.

In the comparative example demonstrated in FIG. 25 , the magnetic fluxdensity changes sharply near the q-axis. The more sharp the change inmagnetic flux density, the more an eddy current generating in the statorwinding 51 will increase. In contrast, the distribution of the magneticflux density in this embodiment has a waveform approximating a sinewave. A change in magnetic flux density near the q-axis is, therefore,smaller than that in the radial anisotropic magnet near the q-axis. Thisminimizes the generation of the eddy current.

The magnet unit 42 creates a magnetic flux oriented perpendicular to themagnetic pole face near the d-axis (i.e., the center of the magneticpole) in each of the magnets 91 and 92. Such a magnetic flux extends inan arc-shape farther away from the d-axis as leaving the magnetic poleface close to the stator 50. The more perpendicular to the magnetic poleface the magnetic flux extends, the stronger the magnetic flux is. Therotating electrical machine 10 in this embodiment is, as describedabove, designed to shape each of the conductor groups 81 to have adecreased thickness in the radial direction, so that the radial centerof each of the conductor groups 81 is located close to the magneticflux-acting surface of the magnet unit 42, thereby causing the strongmagnetic flux to be applied to the stator 50 from the rotor 40. Therotating electrical machine 10 in this embodiment is, as describedabove, designed to shape each of the conductor groups 81 to have adecreased thickness in the radial direction, so that the radial centerof each of the conductor groups 81 is located close to the magnetic poleface of the magnet unit 42, thereby causing the strong magnetic flux tobe applied to the stator 50 from the rotor 40.

The stator 50 has the cylindrical stator core 52 arranged radiallyinside the stator winding 51, that is, on the opposite side of thestator winding 51 to the rotor 40. This causes the magnetic fluxextending from the magnetic flux-acting surface of each of the magnets91 and 92 to be attracted by the stator core 52, so that it circulatesthrough the magnetic path partially including the stator core 52. Thisenables the orientation of the magnetic flux and the magnetic path to beoptimized.

The structure of a control system for controlling an operation of therotating electrical machine 10 will be described below. FIG. 26 is anelectrical circuit diagram of the control system for the rotatingelectrical machine 10. FIG. 27 is a functional block diagram whichillustrates control steps performed by the controller 110.

FIG. 26 illustrates two sets of three-phase windings 51 a and 51 b. Thethree-phase winding 51 a includes a U-phase winding, a V-phase winding,and a W-phase winding. The three-phase winding 51 b includes an X-phasewinding, a Y-phase winding, and a Z-phase winding. The first inverter101 and the second inverter 102 are provided as electrical powerconverters for the three-phase windings 51 a and 51 b, respectively. Theinverters 101 and 102 are made of bridge circuits with as many upper andlower arms as the phase-windings. The current delivered to the phasewindings of the stator winding 51 is regulated by turning on or offswitches (i.e., semiconductor switches) mounted on the upper and lowerarms.

The dc power supply 103 and the smoothing capacitor 104 are connectedparallel to the inverters 101 and 102. The dc power supply 103 is madeof, for example, a plurality of series-connected cells. The switches ofthe inverters 101 and 102 correspond to the semiconductor modules 66 inFIG. 1 . The capacitor 104 corresponds to the capacitor module 68 inFIG. 1 .

The controller 110 is equipped with a microcomputer including a CPU andmemories and works to perform control energization by turning on or offthe switches of the inverters 101 and 102 using several types ofmeasured information measured in the rotating electrical machine 10 orrequests for a motor mode or a generator mode of the rotating electricalmachine 10. The controller 110 corresponds to the control device 77shown in FIG. 6 . The measured information about the rotating electricalmachine 10 includes, for example, an angular position (i.e., anelectrical angle) of the rotor 40 measured by an angular positionsensor, such as a resolver, a power supply voltage (i.e., voltageinputted into the inverters) measured by a voltage sensor, andelectrical current delivered to each of the phase-windings, as measuredby a current sensor. The controller 110 produces and outputs anoperation signal to operate each of the switches of the inverters 101and 102. A request for electrical power generation is a request fordriving the rotating electrical machine 10 in a regenerative mode, forexample, in a case where the rotating electrical machine 10 is used as apower source for a vehicle.

The first inverter 101 is equipped with a series-connected part made upof an upper arm switch Sp and a lower arm switch Sn for each of thethree-phase windings: the U-phase winding, the V-phase winding, and theW-phase winding. The upper arm switches Sp are connected athigh-potential terminals thereof to a positive terminal of the dc powersupply 103. The lower arm switches Sn are connected at low-potentialterminals thereof to a negative terminal (i.e., ground) of the dc powersupply 103. Intermediate joints of the upper arm switches Sp and thelower arm switches Sn are connected to ends of the U-phase winding, theV-phase winding, and the W-phase winding. The U-phase winding, theV-phase winding, and the W-phase winding are connected in the form of astar connection (i.e., Y-connection). The other ends of the U-phasewinding, the V-phase winding, and the W-phase winding are connected witheach other at a neutral point.

The second inverter 102 is, like the first inverter 101, equipped with aseries-connected part made up of an upper arm switch Sp and a lower armswitch Sn for each of the three-phase windings: the X-phase winding, theY-phase winding, and the Z-phase winding. The upper arm switches Sp areconnected at high-potential terminals thereof to the positive terminalof the dc power supply 103. The lower arm switches Sn are connected atlow-potential terminals thereof to the negative terminal (i.e., ground)of the dc power supply 103. Intermediate joints of the upper armswitches Sp and the lower arm switches Sn are connected to ends of theX-phase winding, the Y-phase winding, and the Z-phase winding. TheX-phase winding, the Y-phase winding, and the Z-phase winding areconnected in the form of a star connection (i.e., Y-connection). Theother ends of the X-phase winding, the Y-phase winding, and the Z-phasewinding are connected with each other at a neutral point.

FIG. 27 illustrates a current feedback control operation to controlelectrical currents delivered to the U-phase winding, the V-phasewinding, and the W-phase winding and a current feedback controloperation to control electrical currents delivered to the X-phasewinding, the Y-phase winding, and the Z-phase winding. The controloperation for the U-phase winding, the V-phase winding, and the W-phasewinding will first be discussed.

In FIG. 27 , the current command determiner 111 uses a torque-dq map todetermine current command values for the d-axis and the q-axis using atorque command value in the motor mode of the rotating electricalmachine 10 (which will also be referred to as a motor-mode torquecommand value), a torque command value in the generator mode of therotating electrical machine 10 (which will be referred to as agenerator-mode torque command value), and an electrical angular velocityω derived by differentiating an electrical angle θ with respect to time.The current command determiner 111 is shared between the U-, V-, andW-phase windings and the X-, Y-, and W-phase windings. Thegenerator-mode torque command value is a regenerative torque commandvalue in a case where the rotating electrical machine 10 is used as apower source of a vehicle.

The d-q converter 112 works to convert currents (i.e., three phasecurrents), as measured by current sensors mounted for the respectivephase windings, into a d-axis current and a q-axis current that arecomponents in a two-dimensional rotating Cartesian coordinate system inwhich a d-axis is defined as a direction of an axis of a magnetic fieldor field direction.

The d-axis current feedback control device 113 determines a commandvoltage for the d-axis as a manipulated variable for bringing the d-axiscurrent into agreement with the current command value for the d-axis ina feedback mode. The q-axis current feedback control device 114determines a command voltage for the q-axis as a manipulated variablefor bringing the q-axis current into agreement with the current commandvalue for the q-axis in a feedback mode. The feedback control devices113 and 114 calculate the command voltage as a function of a deviationof each of the d-axis current and the q-axis current from acorresponding one of the current command values using PI feedbacktechniques.

The three-phase converter 115 works to convert the command values forthe d-axis and the q-axis into command values for the U-phase, V-phase,and W-phase windings. Each of the devices 111 to 115 is engineered as afeedback controller to perform a feedback control operation for afundamental current in the d-q transformation theory. The commandvoltages for the U-phase, V-phase, and W-phase windings are feedbackcontrol values.

The operation signal generator 116 uses the known triangle wave carriercomparison to produce operation signals for the first inverter 101 as afunction of the three-phase command voltages. Specifically, theoperation signal generator 116 works to produce switch operation signals(i.e., duty signals) for the upper and lower arms for the three-phasewindings (i.e., the U-, V-, and W-phase windings) under PWM controlbased on comparison of levels of signals derived by normalizing thethree-phase command voltages using the power supply voltage with a levelof a carrier signal, such as a triangle wave signal.

The same structure as described above is provided for the X-, Y-, andZ-phase windings. The d-q converter 122 works to convert currents (i.e.,three phase currents), as measured by current sensors mounted for therespective phase windings, into a d-axis current and a q-axis currentthat are components in the two-dimensional rotating Cartesian coordinatesystem in which the d-axis is defined as the direction of the axis ofthe magnetic field.

The d-axis current feedback control device 123 determines a commandvoltage for the d-axis. The q-axis current feedback control device 124determines a command voltage for the q-axis. The three-phase converter125 works to convert the command values for the d-axis and the q-axisinto command values for the X-phase, Y-phase, and Z-phase windings. Theoperation signal generator 126 produces operation signals for the secondinverter 102 as a function of the three-phase command voltages.Specifically, the operation signal generator 126 works to switchoperation signals (i.e., duty signals) for the upper and lower arms forthe three-phase windings (i.e., the X-, Y-, and Z-phase windings) basedon comparison of levels of signals derived by normalizing thethree-phase command voltages using the power supply voltage with a levelof a carrier signal, such as a triangle wave signal.

The driver 117 works to turn on or off the switches Sp and Sn in theinverters 101 and 102 in response to the switch operation signalsproduced by the operation signal generators 116 and 126.

Subsequently, a torque feedback control operation will be describedbelow. This operation is to increase an output of the rotatingelectrical machine 10 and reduce torque loss in the rotating electricalmachine 10, for example, in a high-speed and high-output range whereinoutput voltages from the inverters 101 and 102 rise. The controller 110selects one of the torque feedback control operation and the currentfeedback control operation and performs the selected one as a functionof an operating condition of the rotating electrical machine 10.

FIG. 28 shows the torque feedback control operation for the U-, V-, andW-phase windings and the torque feedback control operation for the X-,Y-, and Z-phase windings. In FIG. 28 , the same reference numbers asemployed in FIG. 27 refer to the same parts, and explanation thereof indetail will be omitted here. The control operation for the U-, V-, andW-phase windings will be first described.

The voltage amplitude calculator 127 works to calculate a voltageamplitude command that is a command value of a degree of a voltagevector as a function of the motor-mode torque command value or thegenerator-mode torque command value for the rotating electrical machine10 and the electrical angular velocity ω derived by differentiating theelectrical angle θ with respect to time.

The torque calculator 128 a works to estimate a torque value in theU-phase, V-phase, or the W-phase as a function of the d-axis current andthe q-axis current converted by the d-q converter 112. The torquecalculator 128 a may be designed to calculate the voltage amplitudecommand using a map listing relations among the d-axis current, theq-axis current, and the voltage amplitude command.

The torque feedback controller 129 a calculates a voltage phase commandthat is a command value for a phase of the voltage vector as amanipulated variable for bringing the estimated torque value intoagreement with the motor-mode torque command value or the generator-modetorque command value in the feedback mode. Specifically, the torquefeedback controller 129 a calculates the voltage phase command as afunction of a deviation of the estimated torque value from themotor-mode torque command value or the generator-mode torque commandvalue using PI feedback techniques.

The operation signal generator 130 a works to produce the operationsignal for the first inverter 101 using the voltage amplitude command,the voltage phase command, and the electrical angle θ. Specifically, theoperation signal generator 130 a calculates the command values for thethree-phase windings based on the voltage amplitude command, the voltagephase command, and the electrical angle θ and then generates switchingoperation signals for the upper and lower arms for the three-phasewindings by means of PWM control based on comparison of levels ofsignals derived by normalizing the three-phase command voltages usingthe power supply voltage with a level of a carrier signal, such as atriangle wave signal.

The operation signal generator 130 a may alternatively be designed toproduce the switching operation signals using pulse pattern informationthat is map information about relations among the voltage amplitudecommand, the voltage phase command, the electrical angle θ, and theswitching operation signal, the voltage amplitude command, the voltagephase command, and the electrical angle θ.

The same structure as described above is provided for the X-, Y-, andZ-phase windings. The torque calculator 128 b works to estimate a torquevalue in the X-phase, Y-phase, or the Z-phase as a function of thed-axis current and the q-axis current converted by the d-q converter122.

The torque feedback controller 129 b calculates a voltage phase commandas a manipulated variable for bringing the estimated torque value intoagreement with the motor-mode torque command value or the generator-modetorque command value in the feedback mode. Specifically, the torquefeedback controller 129 b calculates the voltage phase command as afunction of a deviation of the estimated torque value from themotor-mode torque command value or the generator-mode torque commandvalue using PI feedback techniques.

The operation signal generator 130 b works to produce the operationsignal for the second inverter 102 using the voltage amplitude command,the voltage phase command, and the electrical angle θ. Specifically, theoperation signal generator 130 b calculates the command values for thethree-phase windings based on the voltage amplitude command, the voltagephase command, and the electrical angle θ and then generates theswitching operation signals for the upper and lower arms for thethree-phase windings by means of PWM control based on comparison oflevels of signals derived by normalizing the three-phase commandvoltages using the power supply voltage with a level of a carriersignal, such as a triangle wave signal. The driver 117 then works toturn on or off the switches Sp and Sn for the three-phase windings inthe inverters 101 and 102 in response to the switching operation signalsderived by the operation signal generators 130 a and 130 b.

The operation signal generator 130 b may alternatively be designed toproduce the switching operation signals using pulse pattern informationthat is map information about relations among the voltage amplitudecommand, the voltage phase command, the electrical angle θ, and theswitching operation signal, the voltage amplitude command, the voltagephase command, and the electrical angle θ.

In operation, the switches Sp and Sn are turned on or off, so that phasecurrents, as illustrated in FIG. 29(a), flow 30° out of phase with eachother in two sets of phase windings, i.e., the three-phase windings 51 aand 51 b. This causes, as demonstrated in FIG. 29(b), the three-phasewinding 51 a to produce torque Tr1 and the three-phase winding 51 b toproduce torque Tr2, thereby effectively reducing pulsation of the 6^(th)harmonic component of torque produced by the rotating electrical machine10.

The above described embodiment offers the following beneficialadvantages.

The bearings 21 and 22 are usually subjected to friction during rotationof the rotor 40, and therefore generate heat. The heat would be anobstruction to dissipation of heat from the stator winding 51 disposedin the rotor body 41 or from the electrical components 62. Accordingly,the rotating electrical machine 10 is designed to have the bearings 21and 22 offset from the axial center of the rotor 40 to one of ends ofthe axis of the rotor 40. In other words, the bearings 21 and 22 arearranged only one of the ends of the rotor 40 in a cantilever form. Thiscauses the heat generated from the bearings 21 and 22 during rotation ofthe rotor 40 to concentrate on only one of the ends of the rotor 40,thereby eliminating an obstruction to the dissipation of heat.

The concentration of the heat, as generated from the bearings 21 and 22during rotation of the rotor 40, on only one of the ends of the axis ofthe rotor 40 will result in a difference in temperature in the axialdirection of the rotor 40. This facilitates flow of air from thebearings 21 and 22 toward the rotor 40, thereby improving effectivenessin dissipating the heat from behind the bearings 21 and 22 even when theelectrical components 62 are mounted in a hollow portion of the rotorbody 41.

The rotor body 41 has an opening located farther away from the bearings21 and 22. This facilitates dissipation of heat from the opening of therotor body 41 even when heating elements, such as the electricalcomponents 62, are disposed inside the rotor body 41.

The cantilever arrangement of the rotating shaft 11 may lead to a riskthat the rotation of the rotor 40 increases swinging or vibration of therotating shaft 11. One of the bearings 21 and 22 is designed to bedifferent in dimension of a gap between each of the outer race 25 andthe inner race 26 and the balls 27 from the other of the bearings 21 and22. This minimizes adverse effects on the bearing unit 20 which arisefrom deflection of the rotor 40 or mechanical vibration of the rotor 40due to imbalance resulting from parts tolerance at a location close tothe center of the rotor 40. The stability in rotation of the rotor 40is, therefore, ensured even in the cantilever arrangement of therotating shaft 11.

In the case of use of the cantilever arrangement, the weight of aportion of the rotor which is far away from the bearings will beincreased, so that the inertia is increased, thereby resulting in anincrease in swinging or vibration of the rotor. The rotor 40 is,therefore, designed in the form of a surface magnet type in which thefirst magnets 91 and the second magnets 92 of the magnet unit 42 aresecured to the rotor body 41. This enables an amount of magnetic metalmaterial used to be decreased as compared with an IPM rotor, therebyresulting in a decrease in inertia. It is, therefore, possible to reducethe swinging or vibration of the rotor 40 even with the use of thecantilever arrangement.

The magnet unit 42 uses the first magnets 91 and the second magnets 92implemented by polar anisotropic magnets and is designed to create aflow of magnetic flux in an annular shape between adjacent N and S-polesin the magnets 91 and 92. The magnetic path, therefore, has an increasedlength, as compared with, for example, radial anisotropic magnets. Adistribution of the magnetic flux density will, therefore, exhibit ashape similar to a sine wave illustrated in FIG. 17 . This facilitatesconcentration of magnetic flux on the magnetic pole, thereby enablingthe degree of torque produced by the rotating electrical machine 10 tobe increased. This also reduces leakage of magnetic flux from thepermanent magnets to make a magnetic circuit in the rotor 40. In otherwords, the function of the rotor 40 to create the magnetic circuit isachieved fully by the permanent magnets.

The rotor body 41 retaining the magnets 91 and 92 exhibiting inertia maybe made of synthetic resin, such as CFRP, not a magnetic metal material.The use of synthetic resin to make the rotor body 41 minimizes theinertia, thereby reducing the swinging or vibration of the rotor 40 inthe cantilever arrangement.

The rotating electrical machine 10 is designed to have the outer rotorstructure in which the rotor 40 is arranged outside the stator 50 in theradial direction. The magnet unit 42 is, therefore, secured to the innerperiphery or inner circumferential surface of the rotor body 41. Thisfirmly retains, unlike the inner rotor structure, the magnet unit 42inside the rotor body 41 against centrifugal force acting on the magnetunit 43 during rotation of the rotor 40. In other words, it is possibleto minimize the size of a structure retaining the magnet unit 42 on therotor body 41 as compared with the inner rotor structure, therebyenabling the inertia to be decreased to minimize the swinging orvibration of the rotor 40 even in the cantilever arrangement.

The intermediate portion 45 has a radially inner portion and a radiallyouter portion which has a difference in level therebetween in the axialdirection. The magnet retainer 43 and the fixing portion 44 partiallyoverlap each other in the axial direction. This results in a decrease indimension of the rotating electrical machine 10 in the axial directionthereof to be decreased and also ensures required dimensions of themagnet retainer 43 and the fixing portion 44 in the axial direction. Theensuring of the required dimension of the fixing portion 44 in the axialdirection enables the bearings 21 and 22 to be arranged at a requiredinterval away from each other, thereby ensuring the stability inoperation of the bearings 21 and 22. This also enables the rotor 40 tobe retained on the rotating shaft 11 around to the center of gravity ofthe rotor as compared with when the intermediate portion 45 is shaped tobe flat without any difference in level, thereby achieving the stabilityin operation of the rotor 40.

The rotating electrical machine 10 is designed to have a slot-lessstructure in which there is no soft magnetic material-made tooth betweenthe conductors 82 arranged adjacent each other in the circumferentialdirection. Each of the conductors 82 has the conductor body 82 a made ofan aggregation of the wires 86. This enables the current flow path inthe conductors 82 to be thinned, thereby resulting in an increase inelectrical resistance of the conductors 82 to a flow of eddy currentarising from interlinking of a magnetic field including a harmonicmagnetic field from the magnet unit 42 with the conductors 82. Thisreduces the eddy current flowing through the conductors 82 to decreasethe eddy-current loss.

The conductor body 82 a is, as described above, made of the twistedwires 86, thereby causing each of the wires 86 to have portions wheredirections of applied magnetic field are opposite each other, whichcancels a back electromotive force resulting from the interlinkingmagnetic field. This results in a great reduction in the eddy current todecrease the eddy-current loss.

Particularly, in this embodiment, each of the wires 86 is made of fibersincluding boron-containing microfibers in which carbon in carbonnanotube fibers is at least partially substituted with boron. Thisenables a current flow path in the conductor body 82 a to be madenarrower and also enables the number of times the current flow path istwisted to be increased, thereby minimizing electrical resistance to aflow of the eddy current to enhance a decrease in eddy-current loss.

The conductors 82 of the stator winding 51 are, as described above,flattened, thereby resulting in a decreased thickness of the straightsections 83 in the radial direction, which enables the radial center ofthe straight sections 83 to be located close to the magnet unit 42. Theair gap between the stator core 52 and the magnet unit 42 may also bedecreased by shaping the conductors 82 to be flat to decrease thethickness of the straight sections 83 in the radial direction. Thisreduces the magnetic resistance in the magnetic circuit to a flow ofmagnetic flux passing through the stator 50 and the rotor 40, so thatthe magnetic flux is increased in the magnetic circuit. This decreasesmagnetic saturation in the stator 50 using the slot-less structure andalso enhances the density of magnetic flux in the straight sections 83to increase torque produced by the rotating electrical machine 10.

The torque is, as described above, increased by the flat shape of theconductors 82, but however, the flat shape will result in an increase inamount of magnetic flux traveling from the magnet unit 42 to theconductors 82, thus resulting in an increase in eddy current. Each ofthe conductors 82 in this embodiment is, however, made of an aggregationof the wires 86. The conductor body 82 a is formed by the twisted wires86, thereby further decreasing the eddy current flowing in theconductors 82. The conductors 82 are flattened in the radial direction,thereby also decreasing the eddy current. This embodiment, therefore,serves to increase the torque output from the rotating electricalmachine 10 and reduce the eddy-current loss.

The magnet unit 42 is made up of permanent magnets: the first magnets 91and the second magnets 92, so that the magnet unit 42 generates magneticfield all the time. This causes the magnet unit 42 to produce a rotatingmagnetic field resulting from rotation of the rotor 40 without any loadthereon even when the controller 110 is not driving the rotatingelectrical machine 10, so that the eddy current will flow through theconductors 82 due to a harmonic magnetic field. However, each of theconductors 82 in this embodiment is made of an aggregation of the wires86. Each of the conductor bodies 82 a is formed by the twisted wires 86.This enhances a decrease in eddy current flowing in the conductors 82.It is, therefore, possible to decrease the eddy-current loss even whenthe rotating electrical machine 10 is at rest.

In order to eliminate magnetic saturation in a q-axis core portion, thefirst magnets 91 and the second magnets 92 are mounted on a surface ofthe motor 40 which faces the stator 50. On this condition, polaranisotropic permanent magnets are used to make the first magnets 91 andthe second magnets 92 in order to enhance the torque output from therotating electrical machine 10. This structure increases the torque withan increase in magnetic flux, but results in an increase in amount ofmagnetic flux interlinking with the conductors 82, so that the eddycurrent is increased. This embodiment, however, has the conductors 82each of which is made of an aggregation of the wires 86 and also has theconductor bodies 82 a each of which is made of the twisted wires 86,thereby more effectively decreasing the eddy current flowing through theconductors 82. The rotating electrical machine 10 in this embodiment is,therefore, capable of increasing the torque output and reducing theeddy-current loss.

The rotating electrical machine 10 is designed to have a first region X1and a second region X2. The first region X1 is a region located radiallyinside an inner periphery of a magnetic circuit component including thestator 50 and the rotor 40. The second region X2 is a region radiallyextending from the inner periphery of the magnetic circuit component tothe housing 30. The volume of the first region X1 is larger than that ofthe second region X2, so that the dissipation of heat is morefacilitated in the first region X1 than the second region X2, therebyproviding a suitable heat dissipation ability.

The first region X1 is smaller in transverse sectional area than thesecond region X2. Specifically, if a radius of an inner peripheralsurface of the housing 30 is defined as d, the magnetic circuitcomponent is located at a distance from the center of rotation of therotor 40 which is greater than d×0.705 in the radial direction. Asviewed in a region where the magnet unit 42 of the rotor 40 overlaps thestator winding 51 in the axial direction, the volume of the first regionX1 is larger than that of the second region X2. This enhances the heatdissipation ability.

The intermediate portion 45 is offset from the center of the rotor 40 inthe axial direction of the rotor 40. This layout enables the firstregion X1 to have an increased volume as compared with when theintermediate portion 45 is located at the center of the rotor 40 or whenintermediate portions are offset from the center of the rotor 40 inopposite axial direction. The offset layout of the intermediate portion45 from the center of the rotor 40 in the axial direction enables therotor 40 has an opening located away from the intermediate portion 45 tofacilitate the dissipation of heat therefrom. This enhances the heatdissipation ability.

The rotor 40 has the outer rotor structure in which the rotor 40 islocated radially outside the stator 50. The magnet unit 42 is secured tothe radially inner periphery of the rotor body 41. This holds themagnetic unit 42, unlike the inner rotor structure, from beingaccidentally removed from the rotor 40 when subjected to centrifugalforce during rotation of the rotor 40, thereby ensuring the stability inretaining the magnet unit 42 to the inner periphery of the rotor body41. Therefore, it is possible to decrease the number of parts requiredto secure the magnet unit 42 to the rotor body 41 as compared with theinner rotor structure. For instance, a surface magnet type rotor 40 maybe used, thereby enabling the rotor 40 to be thinner than the innerrotor structure, which also enables the first region X1 and the secondregion X2 to have increased sizes.

The unit base 61 is provided which serves as a stator retainer forretaining the stator 50. The unit base 61 includes the cylinder 71secured to a radially inner periphery of the stator 50. The cylinder 71has formed therein the coolant path 74 (corresponding to a coolingportion) through which coolant flows. The coolant path 74 serves todissipate heat from the magnetic circuit component to cool the magneticcircuit component and also to release heat from the electricalcomponents 62 disposed in the first region X1 radially inside thecylinder 71. The coolant path 74 has the cooling ability to sufficientlycool the magnetic circuit component. In other words, the first region X1is larger in size than the second region X2, thereby facilitating thedissipation of heat from the electrical components 62 including heatgenerating parts or members (e.g., the semiconductor modules 66) in thefirst region X1 which generate an amount of heat equal to or less thanthat generated by the magnetic circuit component.

The electrical components 62 include the heat generating parts ormembers (i.e., the semiconductor modules 66 and the capacitor modules68) when energized. The semiconductor modules 66 are arranged along theinner peripheral surface of the cylinder 71. The coolant path 74 isarranged to overlap the semiconductor modules 66 in the radialdirection. The coolant path 74, therefore, serves to dissipate heat fromthe magnetic circuit component (i.e., the rotor 40 and the stator 50)and also from the electrical components 62.

The semiconductor modules 66 constitute an inverter circuit and includesemiconductor switching devices. When turned on or off, thesemiconductor modules 66 usually generates electromagnetic waves. Theelectrical components 62, therefore, corresponds to electromagneticwave-generating members. The electrical components 62 are arranged in avoid space surrounded by the casing 64. The housing 30, the rotor 40,and the stator 50 are arranged outside the casing 64 in the form oflayers. This layout effectively blocks electromagnetic noise generatedby the inverter circuit.

The stator 50 is of the slot-less structure, thereby enabling the statorwinding 51 to have an increased conductive area which reduces the amountof heat generated therefrom. The stator 50 is also enabled to have adecreased thickness in the radial direction thereof to increase thevolume of the first region X1.

The slot-less structure results in an increased conductive density ofthe stator winding 51. The stator winding 51, therefore, uses anisotropyconductors. Specifically, the conductor 82 of the stator winding 51 hasthe conductor body 82 a made of the twisted wires 86. The conductor body82 a is covered with the insulating coating 82 b. This facilitatesinsulating design.

The rotor 40 and the stator 50 are configured to have an air gaptherebetween which meets a relation of D/P<12.2 where D is an outerdiameter of the air gap, and P is the number of magnetic poles.Specifically, the rotor 40 has an inner diameter D (i.e., the outerdiameter of the air gap between the rotor 40 and the stator 50). Therotating electrical machine 10 has the number of magnetic poles P (i.e.,16 in this embodiment). D/P is selected to be 12.2 or less to form thefirst region X1 larger than the second region X2.

The rotor 40 is a surface magnet rotor to which permanent magnets (i.e.,the magnet unit 42) firmly secured to the rotor body 41. This minimizesa used amount of magnetic metallic material, such as iron, and enablesthe rotor 40 to be thin.

The magnet unit 42 uses the first magnets 91 and the second magnets 92that are polar anisotropic magnets. The first and second magnets 91 and92 are engineered to create a magnetic flux flowing in an annular shapebetween a respective adjacent two of the N-poles and the S-poles of themagnets 91 and 92, so that each of the magnetic paths has an increasedlength, as compared with, for example, radial anisotropic magnets. Adistribution of the magnetic flux density will, therefore, exhibit ashape similar to a sine wave illustrated in FIG. 24 . This facilitatesconcentration of magnetic flux around the magnetic poles, therebyenabling the degree of torque produced by the rotating electricalmachine 10 to be increased. Additionally, only use of the permanentmagnets reduces the leakage of magnetic flux to develop a magneticcircuit in the rotor 40. In other words, the function of the rotor 40 tocreate the magnetic circuit is achieved fully by the permanent magnets.This enables the surface magnet type rotor to be used to increase therequired torque output and also enables the rotor 40 to be thin, whichenables the first region X1 to be increased in size and improves thetorque output.

The rotating shaft 11 is retained to be rotatable by a plurality ofbearings 21 and 22 which are arranged away from each other in the axialdirection. The bearings 21 and 22 are offset from the center of therotor 40 to the same side in the axial direction. In other words, thebearings 21 and 22 are offset to the same side in the axial direction inthe cantilever form. The cantilever form causes heat, as produced fromthe bearings 21 and 22, to concentrate on the same side in the axialdirection, thereby facilitating dissipation of heat from the oppositeside to the bearings 21 and 22 even when the electrical components 62including heat generating members, such as the capacitor modules 68 aredisposed in the first region X1.

Modification of First Embodiment

The rotor body 41 of the rotor 40 in the above embodiment is equippedwith the intermediate portion 45 which has a difference in level in theaxial direction, however, the rotor body 41 may alternatively bedesigned to have the flat intermediate portion 45 without the differencein level.

The present invention may be, as illustrated in FIG. 31 , used with aninner rotor rotating electrical machine (i.e., an inward rotating type).In this case, the stator 50 and the rotor 40 are arranged radiallyinward in this order within the housing 30. The inverter unit 60 may bemounted radially inside the rotor 40.

The rotor 40 may be, as illustrated in FIG. 32 , equipped with the aircooling fins 98 which creates flows of air to dissipate heat.

In the above embodiment, precompression may be applied from the side ofthe rotor 40 to the outer race 25 of the bearing 22 which is locatedcloser to the center of the rotor 40 in the axial direction. Forinstance, the annular spacer 9 is, as illustrated in FIG. 33 , disposedbetween the bearing 21 and the bearing 22. The spacer 99 has the annularprotrusion 99 a oriented toward the outer race 25 of the bearing 22. Theprotrusion 99 a has an inner diameter larger than an outer diameter ofthe inner race 26 of the bearing 22 and smaller than an outer diameterof the outer race 25. An elastic member EP, such as a disc spring, isdisposed between the inner shoulder 23 a formed radially inside theretainer 23 and the spacer 99. The precompression is exerted on thespacer 99 toward the bearing 22, so that it is applied only to the outerrace 25 of the bearing 22 to urge the outer race 25 toward the rotor 40in the axial direction. This results in there being no clearance in thebearing 22, thereby reducing vibration of the bearing 22.

Other embodiments will be described below in terms of differencesbetween themselves and the first embodiment.

Second Embodiment

In this embodiment, the polar anisotropic structure of the magnet unit42 of the rotor 40 is changed and will be described below in detail.

The magnet unit 42 is, as clearly illustrated in FIGS. 34 and 35 , madeusing a magnet array referred to as a Halbach array. Specifically, themagnet unit 42 is equipped with the first magnets 131 and the secondmagnets 132. The first magnets 131 have a magnetization direction (i.e.,an orientation of a magnetization vector thereof) oriented in the radialdirection of the magnet unit 42. The second magnets 132 have amagnetization direction (i.e., an orientation of the magnetizationvector thereof) oriented in the circumferential direction of the magnetunit 42. The first magnets 131 are arrayed at a given interval away fromeach other in the circumferential direction. Each of the second magnets132 is disposed between the first magnets 131 arranged adjacent eachother in the circumferential direction. The first magnets 131 and thesecond magnets 132 are each implemented by a rare-earth permanentmagnet, such as a neodymium magnet.

The first magnets 131 are arranged away from each other in thecircumferential direction so as to have N-poles and S-poles which arecreated in radially inner portions thereof and face the stator 50. TheN-poles and the S-poles are arranged alternately in the circumferentialdirection. The second magnets 132 are arranged to have N-poles andS-poles alternately located adjacent the first magnets 131 in thecircumferential direction. Specifically, the first magnets 131 includethe first A magnet 131A whose magnetization direction is orientedradially outward and the first B magnet 131B whose magnetizationdirection is oriented radially inward. The second magnets 132 includethe second A magnet 132A whose magnetization direction is oriented in afirst one of opposite circumferential directions and the second B magnet132B whose magnetization direction is oriented in a second one of theopposite circumferential directions. The magnet unit 42 is configured tohave the first A magnet 131A, the second A magnet 132A, the first Bmagnet 131B, the second B magnet 132B, the first A magnet 131A . . .which are arrayed in this order in the circumferential direction.

The magnet retainer 43 is made of a soft magnetic material and forms amagnetic path. The magnet retainer 43 minimizes leakage of magnetic fluxfrom the first magnet 131 or the second magnet 132 outward in the radialdirection (away from the stator 50) and directs a flow of the magneticflux inwardly in the radial direction, thereby enhancing the density ofmagnetic flux from the first magnet 131 and the second magnet 132inwardly in the radial direction.

The recesses 136 are provided radially outside the first magnets 131, inother words, near the magnet retainer 43 of the rotor body 41. Therecesses 136 are hollowed radially inwardly toward the stator 50. Morespecifically, the magnet unit 42 has end surfaces (i.e., the magneticpole faces 131 a) of the first magnets 131 which face away from thestator 50 and end surfaces (i.e., the side surfaces 132 b) of the secondmagnets 132 which face away from the rotor 50. At least one of themagnetic pole face 131 a and the side surface 132 b defines each of therecesses 136 hollowed toward the stator 50. Specifically, the recesses136 are arranged so that the radially outward magnetic pole faces 131 aof the first magnets 131 and the radially outer side surfaces 132 b ofthe second magnets 132 arranged adjacent the first magnets 131 arearranged alternately in the radial direction. In this embodiment, themagnetic pole faces 131 a of all the first magnets 131 are located moreradially inwardly than the side surfaces 132 b of the second magnets 132toward the stator 50 to define the recesses 136. In other words, therecesses 126 are arranged radially outside the first magnets 131. Eachof the recesses 136 has a length in the circumferential direction whichis equivalent to that of the first magnet 131 (especially, a dimensionof an outer periphery of the first magnet 131).

The magnetic member 133 made of a soft magnetic material is disposed ineach of the recesses 136. In other words, the magnetic members 133 madeof a soft magnetic material are arranged radially outside the firstmagnets 131, i.e., inside the magnet retainer 43 of the rotor body 41.For instance, each of the magnetic members 133 may be made of magneticsteel sheet, soft iron, or a dust core.

Each of the recesses 136 has a length in the circumferential directionwhich is equivalent to that of the first magnet 131 (especially, adimension of the outer periphery of the first magnet 131). An assemblyof the first magnet 131 and the magnetic member 133 has a thickness inthe radial direction which is equivalent to that of the second magnet132 in the radial direction. In other words, the first magnets 131 has athickness smaller than that of the second magnet 132 by that of themagnetic member 133 in the radial direction. Each of the magneticmembers 133 fully occupies a corresponding one of the recesses 136. Eachof the magnets 131 and 132 is firmly joined to the magnetic member 133using, for example, adhesive. In the magnet unit 42, the radial outsideof the first magnets 131 faces away from the stator 50. The magneticmembers 133 are located on the opposite side of the first magnets 131 tothe stator 50 in the radial direction.

Each of the magnetic members 133 has the key 134 in a convex shape whichis formed on the outer periphery thereof and protrudes radially outsidethe magnetic member 133, in other words, protrudes into the magnetretainer 43 of the rotor body 41. The magnet retainer 43 has the keygrooves 135 which are formed in an inner peripheral surface thereof in aconcave shape and in which the keys 134 of the magnetic members 133 arefit. The protruding shape of the keys 134 is contoured to conform withthe recessed shape of the key grooves 135. As many of the key grooves135 as the keys 134 of the magnetic members 133 are formed. Theengagement between the keys 134 and the key grooves 135 serves toeliminate misalignment or a positional deviation of the first magnets131, the second magnets 132, and the rotor body 41 in thecircumferential direction (i.e. a rotational direction). The keys 134and the key grooves 135 (i.e., convexities and concavities or engagingportions and disengaged portions) may be formed either on the magnetretainers 43 of the rotor body 41 or in the magnetic members 133,respectively. Specifically, the magnetic members 133 may have the keygrooves 135 in the outer periphery thereof, while the magnet retainer 43of the rotor body 41 may have the keys 134 formed on the inner peripherythereof.

The magnet unit 42 has the first magnets 131 and the second magnets 132alternately arranged to increase the magnetic flux density in the firstmagnets 131. This results in concentration of magnetic flux on onesurface of the magnet unit 42 to enhance the magnetic flux close to thestator 50.

The layout of the magnetic members 133 radially arranged outside thefirst magnets 131, in other words, farther away from the stator 50reduces partial magnetic saturation occurring radially outside the firstmagnets 131, thereby alleviating a risk of demagnetization in the firstmagnets 131 arising from the magnetic saturation. This results in anincrease in magnetic force produced by the magnet unit 42. In otherwords, the magnet unit 42 in this embodiment has portions which areusually subjected to demagnetization and replaced by the magneticmembers 133.

FIGS. 36(a) and 36(b) are illustrations which demonstrate flows ofmagnetic flux in the magnet unit 42. FIG. 36(a) illustrates aconventional structure in which the magnet unit 42 is not equipped withthe magnetic members 133. FIG. 36(b) illustrates the structure in thisembodiment in which the magnet unit 42 is equipped with the magneticmembers 133. FIGS. 36(a) and 36(b) are linearly developed views of themagnet retainer 43 of the magnet holder 41 and the magnet unit 42. Lowersides of FIGS. 36(a) and 36(b) are close to the stator 50, while uppersides thereof are farther away from the stator 50.

In the structure shown in FIG. 36(a), the magnetic pole face of each ofthe first magnets 131 and a side surface of each of the second magnets132 are placed in contact with the inner peripheral surface of themagnet retainer 43. Each of the first magnets 91 and the second magnets92 usually has a magnetic flux density higher on the magnetic pole facethan in the center of the magnetic pole thereof. In the structure ofFIG. 36(a), an end of the magnetic pole face 131 a of the first magnet131 and an end of the magnetic pole face 132 a of the second magnet 132are close to each other on a surface of contact (i.e., a boundary)between the first magnet 131 and the second magnet 132, thus leading toa risk that magnetic saturation occurs near the surface of contactbetween the first magnet 131 and the second magnet 132 in the magnetretainer 43.

In the magnet retainer 43, a combined magnetic flux is created which ismade up of a magnetic flux F1 which passes outside the second magnet 132and then enters the surface of the first magnets 131 contacting themagnet retainer 43 and a magnetic flux which flows substantiallyparallel to the magnet retainer 43 and attracts a magnetic flux F2produced by the second magnet 132. A magnetic flux passing through themagnet retainer 43 bypasses a portion of the magnet retainer 43 wheremagnetic saturation partially occurs (i.e., near a surface of contactbetween the first magnets 131 and the second magnets 132). This resultsin an increase in magnetic path passing through the magnet retainer 43which may lead to demagnetization.

In the structure in FIG. 36(b), each of the recesses 136 is arranged sothat the end surface (i.e., the magnetic pole face 131 a) of the firstmagnets 131 and the end surface (i.e., the side surface 132 b) of thesecond magnet 132 which contacts the first magnet 131 radially outsidethe second magnet 132 are offset from each other in the radialdirection. In other words, ends or corners of the magnetic pole faces131 a of the first magnet 131 and the magnetic pole surface 132 a of thesecond magnet 132 are located away from each other, thereby minimizing arisk that magnetic saturation may occur in a portion of the magnetretainer 43 near the contact between the first magnet 131 and the secondmagnet 132, in other words, decreasing the magnetic saturation in themagnet retainer 43 which deflects flows of magnetic flux, therebyresulting in an increase in resistance to demagnetization.

Each of the magnetic members 133 is disposed in space defined by therecess 136. This facilitates flow of magnetic flux through the magneticmember 133 and the magnet retainer 43 radially outside the magnet unit42 between the first A magnet 131A and the first B magnet 131B.Accordingly, the magnetic members 133 fully occupying the recesses 136serve to facilitate the flow of magnetic flux more as compared with whenthe recesses 136 are filled with non-magnetic members or air. Themagnetic member 133 also facilitates flow of magnetic flux, as emergingfrom the magnetic pole face 132 a of the second magnets 132, toward themagnetic pole face 131 a of the first magnet 131. This ensures passageof magnetic flux, as produced by the first magnets 131 or the secondmagnets 132, through the magnet retainer 43 and the magnetic members133.

The structure in FIG. 36(b), unlike FIG. 36(a), functions to eliminatethe magnetic flux F2 inducing the magnetic saturation. This effectivelyenhances the permeance in the whole of the magnetic circuit, therebyensuring the stability in properties of the magnetic circuit underelevated temperature.

As compared with radial magnets used in conventional SPM rotors, thestructure in FIG. 36(b) has an increased length of the magnetic pathpassing through the magnet. This results in a rise in permeance of themagnet which enhances the magnetic force to increase the torque.Further, the magnetic flux concentrates on the center of the d-axis,thereby increasing the sine wave matching percentage. Particularly, theincrease in torque may be achieved effectively by shaping the waveformof the current to a sine or trapezoidal wave under PWM control or using120° excitation switching ICs

Specifically, the magnetic density distribution, as illustrated in FIG.37 , becomes approximately a sine wave, thereby resulting inconcentration of magnetic flux on the magnetic pole, unlike a magneticdensity distribution of radial anisotropic magnets shown in thecomparative example of FIG. 25 , which enhances torque output from therotating electrical machine 10. In FIG. 37 , a horizontal axis indicatesthe electrical angle, while a vertical axis indicates the magnetic fluxdensity. 90° on the horizontal axis represents the d-axis (i.e., thecenter of the magnetic pole). 0° and 180° on the horizontal axisrepresent the q-axis.

In the comparative example demonstrated in FIG. 25 , the magnetic fluxdensity changes sharply near the q-axis. The more sharp the change inmagnetic flux density, the more an eddy current generating in the statorwinding 51 will increase. In contrast, the distribution of the magneticflux density in this embodiment has a waveform approximating a sinewave. A change in magnetic flux density near the q-axis is, therefore,smaller than that in the radial anisotropic magnet near the q-axis. Thisminimizes the generation of the eddy current. The sine wave matchingpercentage in the distribution of the magnetic flux density ispreferably set to, for example, 40% or more. This improves the amount ofmagnetic flux around the center of a waveform of the distribution of themagnetic flux density as compared with a radially oriented magnet or aparallel oriented magnet in which the sine wave matching percentage isapproximately 30%.

The magnet unit 42 creates a magnetic flux oriented perpendicular to themagnetic pole face near the d-axis of each of the magnets 131 and 132(i.e., the center of the magnetic pole). Such a magnetic flux extends inan arc-shape farther away from the d-axis, farther from the magneticpole face. The more perpendicular to the magnetic pole face the magneticflux extends, the stronger the magnetic flux is. The rotating electricalmachine 10 in this embodiment is, as described above, designed to shapeeach of the conductor groups 81 to have a decreased thickness in theradial direction, so that the radial center of each of the conductorgroups 81 is located close to the magnetic pole face of the magnet unit42, thereby causing the strong magnetic flux to be applied to the stator50 from the rotor 40.

The stator 50 has the cylindrical stator core 52 arranged radiallyinside the stator winding 51, that is, on the opposite side of thestator winding 51 to the rotor 40. This causes the magnetic fluxextending from the magnetic pole face of each of the magnets 131 and 132to be attracted by the stator core 52, so that it circulates through themagnetic path partially including the stator core 52. This enables theorientation of the magnetic flux and the magnetic path to be optimized.

The above described second embodiment offers the following beneficialadvantages.

The magnet unit 42 has the recesses 136 each of which is defined by atleast one of the end surface (i.e., the magnetic pole face 131 a) of thefirst magnet 131 which is located away from the stator 50 and the endsurface (i.e., the side surface 132 b) of the second magnet 132 which islocated away from the stator 50. Such an end surface is hollowed towardthe stator 50 to define the recess 136. In other words, the magnet unit42 has formed therein the recesses 136 which orient the radially outsideend surfaces (i.e., the magnetic pole faces 131 a of the first magnets131 and the radially outside end surfaces (i.e., the side surfaces 132b) of the second magnets 132 arranged adjacent the first magnets 131 sothat they are offset from each other in the radial direction. Themagnetic members 133 made of soft magnetic material are disposed in therecesses 136.

With the above layout, the ends or corners of the magnetic pole faces131 a of the first magnets 131 are located away from the ends or cornersof the magnetic pole faces 132 a of the second magnets 132, therebyminimizing a risk that magnetic saturation may occur in a portion of themagnet retainer 43 near the contact between the first magnet 131 and thesecond magnet 132, in other words, decreasing the magnetic saturation inthe magnet retainer 43 which deflects flows of magnetic flux, therebyresulting in an increase in resistance to the demagnetization. Thespaces defined by the recesses 136 are occupied by the magnetic members133 which facilitates flow of magnetic flux through the magnetic member133 and the magnet retainer 43 radially outside the magnet unit 42between the first A magnet 131A and the first B magnet 131B. Themagnetic member 133 also facilitates flow of magnetic flux, as emergingfrom the magnetic pole face 132 a of the second magnets 132, toward themagnetic pole face 131 a of the first magnet 131. This ensures passageof magnetic flux, as produced by the first magnets 131 or the secondmagnets 132, through the magnet retainer 43 and the magnetic members133. Therefore, flows of magnetic flux from the magnets 131 and 132 arefacilitated to improve the magnetic flux density close to the stator 50.

Each of the first magnets 131 whose magnetization direction is orientedradially has a portion which is farther away from the stator 50 and hasthe highest probability of demagnetization. In order to alleviate such aproblem, the above structure is designed to have the end surfaces of allthe first magnets 131 which are hollowed radially inward so that theyare located radially inside the end surfaces of the second magnets 132,thereby defining the recesses 136. The magnetic members 133 are arrangedradially outside the first magnets 131. This minimizes thedemagnetization and enables the volume of the first magnets 131 to bedecreased.

The sum of thicknesses of each of the first magnet 131 and acorresponding one of the magnetic members 133 are selected to be equalto the thickness of each of the second magnets 132 in the radialdirection, thereby facilitating the flow of magnetic flux and improvingthe magnetic flux density.

The magnet retainer 43 made of soft magnetic material is located on anopposite side of the magnet unit 42 to the stator 50 and extends overthe magnets 131 and 132 arranged adjacent each other in thecircumferential direction, thereby minimizing leakage of magnetic fluxfrom the magnet unit 42 away from the stator 50 to improve the magneticflux density close to the stator 50. There is, however, a risk thatmagnetic saturation partially occurs in the magnet retainer 43, therebydemagnetizing the first magnets 131. Such demagnetization is, asdescribed already, alleviated by the magnetic members 133 disposed inthe recesses 136, thereby minimizing the demagnetization of the firstmagnets 131.

The rotor 40 is of an outer rotor structure in which the rotor 40 isarranged radially outside the stator 50, thereby minimizing a risk ofaccidental removable of the magnet unit 42 arising from the centrifugalforce, as compared with an inner rotor structure. This eliminates theneed for an additional stopper to hold the magnet unit 42 from beingremoved. This enables the rotor 40 to have a decreased thickness and anair gap between the stator 50 and the rotor 40 to be reduced in size,thereby enhancing the torque output.

The magnetic members 133 have the keys 134 fit in the magnet retainer43. Specifically, the magnet members 133 which are higher in mechanicalproperties (i.e., rigidity) than typical magnets are designed to havethe keys 134, so that the keys 134 sufficiently function as stoppers tohold the magnetic members 133 from being rotated relative to the magnetretainer 43.

The magnet unit 42 has the first A magnet 131A, the second A magnet132A, the first B magnet 131B, and the second B magnet 132B arrayed inthis order in the circumferential direction. This layout (i.e., magneticflux concentrated layout) enhances the magnetic flux density close tothe stator 50.

The magnet layout in the second embodiment enables a magnetic circuit tobe created in the rotor 40 without leakage of magnetic flux using themagnets 131 and 132. In other words, the function of the rotor 40 tocreate the magnetic circuit is achieved fully only using the magnets 131and 132.

The rotor body 41 retaining the magnets 91 and 92 exhibiting inertiamay, therefore, be made of synthetic resin, such as CFRP, not a magneticmetal material. The use of synthetic resin to make the rotor body 41minimizes the inertia, thereby reducing the swinging or vibration of therotor 40 in the cantilever arrangement.

The function of the rotor 40 to create the magnetic circuit is, asdescribed above, achieved fully only by the magnets 131 and 132. Thisenables the surface magnet type rotor to be used to increase therequired torque output and also enables the rotor 40 to be thin, whichenables the first region X1 to be increased in size and improves thetorque output.

Modification of Second Embodiment

The second embodiment is designed to have the recesses 136 disposed onthe opposite side of the first magnets 131 to the stator 50. Themagnetic members 133 are arranged in the recesses 136. The magneticmembers 133 may alternatively be located on the opposite side of thesecond magnets 132 to the stator 50. For instance, the second magnets132 may be, as illustrated in FIG. 38 , shaped to have a radialthickness smaller than that of the first magnets 131 to create therecesses 136. The magnetic members 133 are mounted in the recesses 136.In other words, the magnetic members 133 are located on the oppositeside of the second magnets 132 to the stator 50. The sum of the radialthicknesses of each of the second magnets 132 and a corresponding one ofthe magnetic members 133 is preferably determined to be equal to theradial thickness of the first magnet 131.

The above structure is capable of minimizing the demagnetization anddecreasing the volume of the second magnets 132. By selecting the sum ofthe radial thicknesses of each of the second magnets 132 and acorresponding one of the magnetic members 133 to be equal to the radialthickness of the first magnet 131, flow of magnetic flux is facilitatedto improve the magnetic flux density.

In the second embodiment, the recesses 136 and the magnetic members 133are provided for both the first A magnet 131A and the first B magnet131B, but however, they may alternatively be provided only for either ofthe first A magnet 131A or the first B magnet 131B whose magnetizationdirection is oriented radially inwardly (i.e., toward the stator 50).This minimizes iron loss and reduction in magnetic field in the rotor40. Similarly, the recesses 136 and the magnetic members 133 mayalternatively be provided only for either of the second A magnet 132A orthe second B magnet 132B. At least one of the first A magnet 131A, thefirst B magnet 131B, the second A magnet 132A, and the second B magnet132B may alternatively be shaped to have the recess 136 which is formedin a surface thereof facing away from the stator 50 and in which themagnetic member 133 is disposed. At least one of end surfaces of thefirst A magnets 131A may alternatively have the recess 136 hollowedtoward the stator 50. The same applies to the first B magnet 131B, thesecond A magnet 132A, or the second B magnet 132B. At least one of endsurfaces of the magnets 131 and 132 may have the recess 136 hollowedtoward the stator 50.

In the second embodiment, the length of the first magnets 131 and thesecond magnets 132 in the circumferential direction may be changed asneeded. For instance, the first magnets 131 may be, as illustrated inFIG. 39 , shaped to be shorter than the second magnets 132. It isadvisable that the length of the second magnets 132 in thecircumferential direction lies in a range of 52<α<80 where α is anelectrical angle [degE] (see FIG. 40 ). The mounting of the magneticmembers 133 usually causes an optimum value of an angle betweencommutating poles that is typically 60 [degE] to be shifted to 68[degE]. This enables the second magnets 132 (i.e., the commutatingpoles) to be designed to lie in the above range to achieve themechanical rotation stop without demagnetization.

In the second embodiment, the keys 134 and the key grooves 135 may beomitted from the magnetic members 133 and the magnet retainer 43.

The magnetic members 133 and the keys 134 are not essential for thesecond embodiment.

In the second embodiment, the magnet retainer 43 is made from a softmagnetic material, but however, may be made from another type ofmaterial.

In the second embodiment, the second magnets 132 may alternatively bedesigned to have a magnetization direction including components orientedin radial and circumferential directions.

Third Embodiment

In this embodiment, the straight sections 83 for the same phase whichare joined by the turns 84 are arranged on the same pitch circle definedabout the axis of the rotor 40. In the following discussion, an intervalbetween the centers of the circumferentially adjacent straight sections83 mounted on the same pitch circle is defined as an arrangement pitchPs. The arrangement pitch Ps will be described below with reference toFIG. 41 . In FIG. 41 , a pitch circle on which the straight sections 83are arranged on the first layer position is expressed by C1. A pitchcircle on which the straight sections 83 are arranged on the secondlayer position is expressed by C2. The arrangement pitch Ps for thestraight sections 83 on the first layer position is expressed by P1. Thearrangement pitch Ps for the straight sections 83 on the second layerposition is expressed by P2. The diameter Ds of the pitch circle C1 onthe first layer position is expressed by DL1. The diameter Ds of thepitch circle C2 on the second layer position is expressed by DL2. FIG.41 illustrates the stator 50 when linearly developed.

If Ds/Ps for each phase is defined as τ, the torque may be increased inan easy way regardless of the size of the rotating electrical machine 10by selecting a value of τ to lie in a suitable range which is, as can beseen in FIG. 42 , set to meet a relation of 24<τ<34. This range isdetermined to increase conductor region/gap region within a range of 20[A/mm{circumflex over ( )}2] to 40[A/mm{circumflex over ( )}2] which isusually set as a maximum electrical current in typical rotatingelectrical machines. This setting realizes the stator winding 51 whichhas a maximum conductor area for the outer diameter of the rotatingelectrical machine 10 and maximizes a density of power inputted to therotating electrical machine 10 as a function of the size thereof. FIG.43 represents a value of τ for the number of magnetic poles Pn in arotating electrical machine equipped with six phase-windings. In thisembodiment, the number of poles of the stator winding 51 is 16, so thatthe value of τ is given by a value when Pn=16. The arrangement pitch Psmay be determined simply using the value of τ once the diameter Ds isderived. The use of the value τ, therefore, minimizes the number ofdesign steps to optimize the interval between the straight sections 83.

The range of τ may be set to 24<τ<38 if there is no need to use therotating electrical machine 10 with vehicles. It is also advisable thatτ be greater than 25. There is no distribution factor for each phase, sothat a winding factor is, for example, one.

The above described embodiment offers the following beneficialadvantages.

The straight sections 83 joined by the turns 84 for the same phase arelocated on the same pitch circle defined about the axial center of therotor 40. An arrangement pitch that is an interval between the centersof the circumferentially adjacent straight sections 83 arranged on thesame pitch circle in the circumferential direction is defined as Ps. Thediameter of the same pitch circle is defined as Ds. Ds/Ps is expressedby τ. The arrangement pitch between the straight sections 83 in thecircumferential direction is determined to meet a relation of 24<τ<34.This causes the straight sections 83 to be arranged close to each otherin the circumferential direction, thereby enhancing the torque output.The use of the value τ enables the locations of the straight sections 83to be determined properly to increase the torque output in the easy wayregardless of the size of the rotating electrical machine and minimizesthe number of design steps to optimize the interval between the straightsections 83. The arrangement pitch, as referred to herein, is a pitchbetween conductors or a pitch between insulating layers of, for example,U-phase, V-phase, and W-phase conductor groups.

The straight sections 83 and the turns 84 may be made from conductivematerial other than copper. In this case, if an electrical resistivityOm of copper is defined as ρ1, an electrical resistivity of a conductivematerial is defined as ρ2, and ρ1/ρ2 is defined as ρs, 24/ρs<τ<34/ρs is,as illustrated in FIGS. 42 and 43, preferably met. When the straightsections 83 and the turns 84 are made from copper, ρs will be equal toone.

The core 52 is assembled with the stator winding 51. The rotatingelectrical machine 10 is of the slot-less structure in which a softmagnetic material-made core is not disposed between thecircumferentially adjacent straight sections 83. The stator core 52which is arranged radially away from the rotor 40 functions as a backyoke to create a magnetic circuit although there is no core between thestraight sections 83. The slot-less structure enables the adjacentstraight sections 83 to be arranged close to each other to increase aconductor sectional area, as compared with when there is a core betweenthe straight sections 83. The slot-less structure also minimizes therisk of magnetic saturation, increases the conductor sectional area, andenables a required magnetic circuit to be developed because there is nocore between the straight sections 83, thereby enabling an electricalcurrent delivered to the stator winding 51 to be increased. Thisenhances the torque output from the rotating electrical machine 10.

The parameter τ indicates a numerical range required to increase thetorque output using the stator winding 51 used in the slot-lessstructure in which the straight sections 83 are arrayed adjacent eachother in the circumferential direction. The parameter τ is a uniqueparameter derived based on technical ideas different to use of anotherparameter defining a numerical range to enhance the torque output.

Modification 1 of the Third Embodiment

In this embodiment, the stator winding 201 is, as illustrated in FIG. 44, made of round conductors. Specifically, the stator winding 201 isequipped with the annular stator core 200 and the conductors includingthe straight sections 211 and the turns 212. The conductors are eachimplemented by a round conductor whose sectional area is circular. Theconductors are bent so that they are arranged in a given layout patternin the circumferential direction, thereby creating phase windings of thestator winding 201. The conductors have the straight sections 211 andthe turns 212 which are arranged alternately in the form of a continuingwave winding. The straight sections 211 face the magnet unit in theradial direction. The straight sections 211 have portions which arearranged at a given interval away from each other axially outside themagnet unit and joined together by the turns 212. In this embodiment thestator winding 201 is wound in the shape of an annular distributedwinding.

The stator winding 201 includes phase windings, one pair for each phase.The three-phase windings are arranged in the form of one layer. In theexample illustrated in FIG. 44 , the number of poles is sixteen. Thestraight sections 211 and the turns 212 are each covered with aninsulating coating to achieve electrical insulation therebetween. Eachof the phase windings made up of the straight sections 211 and the turns212 is insulated by the insulating coating except an exposed portionthereof for joining purposes. The exposed portion includes, for example,an input or an output terminal or a neutral point in a case of a starconnection.

The straight sections 211 which are located at the same position in theradial direction and arranged at 3 pitches away from each other in thecircumferential direction are joined together by the turn 212. In otherwords, outer two of every four adjacent straight sections 211 which arearranged on the same pitch circle defined about the axial center of therotor are connected together by the turn 212. The turns 212 includethree types: the turns 212 a extending in the axial direction, the turns212 b bent outward in the radial direction, and the turns 212 c bentinward in the radial direction. The use of such three types turns servesto avoid physical interference among the turns 212.

The arrangement pitch between the straight sections 211 in thecircumferential direction is determined to meet a relation of 24<τ<34.The circumferentially adjacent straight sections 211 are, therefore,placed in contact with each other.

In this embodiment, the determination of the arrangement pitch in therange of 24<τ<34 enables easy-to-machine round conductors whose aspectratio is less than two to be arranged close to each other between thestator and the rotor within a range of 20 [A/mm{circumflex over ( )}2]to 40[A/mm{circumflex over ( )}2] which is usually set as a maximumelectrical current in typical rotating electrical machines for vehicles.Rectangular conductors may alternatively be used.

If conductors whose aspect ratio is two or more are used out of therange of 24<τ<34, the percentage of extension of copper will be 35% ormore which exceeds an allowable limit of copper, thereby resulting indamage to the copper wire when it is bent. It is, therefore, impossibleto use the copper wire to make the stator winding 201.

The use of the range of 24<τ<34 maximizes the input power densityalthough conductor segments or round conductors are used, therebyavoiding a great increase in production costs without need for alteringa control system for current rotating electrical machines.

FIG. 45 is schematic view which illustrates how to connect the straightsections 211 and the turns 212 for one phase. In FIG. 45 , locations ofthe straight sections 211 are indicated by symbols D1, D4, D7 . . . . Inthis embodiment, the straight sections 211 and the turns 212 are, as canbe seen in FIG. 45 , joined continuously between exposed input andoutput terminals. The positioning of the stator winding 201 in thecircumferential direction is, therefore, achieved by simply engagingportions of the stator winding 201 with protrusions on the stator core200, thereby greatly improving the ease of assembly of the statorwinding 201.

The above protrusions are, as described already, preferably shaped notto protrude radially outside an imaginary circle defined to pass throughradial centers (i.e., centers of circular cross sections) of thestraight sections 211.

Modification 2 of the Third Embodiment

Instead of each of the phase windings formed by a continuing conductormade up of the straight sections 211 and the turns 212, a wave windingfor each phase may be, as illustrated in FIG. 46 , made by welding orsoldering a plurality of (e.g., two) conductors 230 and 240 toelectrically join them. Each of the conductors 230 and 240 includes thestraight sections 211 and the turns 212. In this case, the stator core200 is preferably designed to have more protrusions than the conductors.Each of the protrusions is arranged at a location on the stator whichcorresponds to a location of one of the conductors 230 and 240. Thisstructure facilitates positioning of the conductors 230 and 240 in thecircumferential direction.

Modification 3 of the Third Embodiment

In this embodiment, a rotating electrical machine is of an inner rotortype (i.e., the inward rotating type). FIG. 47 is a longitudinalsectional view along the rotating shaft 301 of the rotating electricalmachine 300.

The rotating electrical machine 300 is equipped with the rotating shaft301, two bearings 302 and 303, the housing 310, the rotor 320, and thestator 330 which are arranged coaxially with each other along with therotating shaft 301.

The bearings 302 and 303 are disposed away from each other in the axialdirection within the housing 310. Each of the bearings 302 and 303 isimplemented by, for example, a radial ball bearing. The bearings 302 and303 retain the rotating shaft 301 and the rotor 320 to be rotatable.

The rotor 320 includes the cylindrical rotor body 321 and the annularmagnet unit 322 mounted on the rotor body 321. The magnet unit 322 ismade up of a plurality of magnets whose magnetic poles are arrangedalternately in the circumferential direction. In this embodiment, therotating electrical machine 300 is of a magnet-embedded type.

The stator 330 is located radially outside the rotor 320. The stator 330includes the cylindrical stator winding 331 and the stator core 332arranged radially outside the stator winding 331. The stator core 332 isof a circular ring shape and arranged radially inside the housing 310.The stator core 332 is secured to the housing 310 using, for example,adhesive. The stator core 332 may be designed, like in the firstembodiment, to have a slot-less structure with no teeth.

The stator winding 331 faces the annular magnet unit 322 through a givenair gap. The stator winding 331 is made of a three-phase winding in theform of a full-pitch distributed winding, but however, may alternativelybe made of another type of winding. Conductors of the stator winding 331are, like in the first embodiment, of a flattened shape. Each of theconductors of the stator winding 331 is, like in the first embodiment,made of an aggregation of a plurality of twisted wires.

This embodiment uses the rotor 320 with thirty two magnetic pole pairs.Inverter units are mounted radially inside the rotor 40 within thehousing 310.

The above embodiment has substantially the same beneficial advantages asthe third embodiment.

Other Modifications of the Third Embodiment

The turns 410 b of each conductor 410 may be, as illustrated in FIG. 48, firmly secured to axially opposed ends of the stator core 400, therebyfirmly attaching the stator winding to the stator core 400. Numeral 410a indicates a straight section of the conductor 410.

The coil housing recess 47 is located near the coil ends. There is,therefore, low restriction to space in which the conductors arearranged. This enables the turns 502, as illustrated in FIG. 49 , tohave a sectional area greater than that of the straight section 501.This results in a decrease in electrical resistance of the turns 502 toincrease the amount of electrical current flowing therethrough, therebyenhancing the torque output. The increase in sectional area facilitatesdissipation of heat from the turns 502.

The increase in sectional area results in an increased size of a surfaceof, for example, the turn 502 contacting the stator core near the coilend, thereby enhancing the firm securement of the stator winding. Thestator winding may be secured to the stator core using, for example,adhesive or rivets made of non-conductive material.

The rotor of the rotating electrical machine may have theembedded-magnet structure shown in FIG. 50 . The rotor 600 includes therotor body 610 and the permanent magnets 620. The rotor body 610 hasformed therein the hole 630 through which a rotating shaft passes. Thisstructure creates a magnetic flux not only on the d-axis on which amagnet-produced magnetic flux directly acts, but also on the q-axis,thereby increasing the strength of magnetic field to enhance the torqueoutput from the rotating electrical machine.

The rotating electrical machine may be used as an induction machine ormotor. In this case, the rotor 700 shown in FIG. 51 may be used. Therotor 700 includes the rotor body 710, the rotor conductors 720 (e.g.,cage conductors), and the plate members 740 working to hold the rotorconductors 720 from being removed. In FIG. 51 , numeral 730 indicates arotating shaft. Numeral 750 indicates a stator core.

The rotor of the rotating electrical machine may be equipped with afield winding or a combination of a field winding and permanent magnets.Such a rotor may be, as illustrated in FIG. 52 , implemented by therotor 800 equipped with the Lundell pole core 810. In FIG. 52 , numeral820 indicates a hole through which a rotating shaft passes. In thisstructure, magnetic flux around the d-axis is created by a mixture ofmagnet-produced magnetic flux and excited magnetic flux, therebyincreasing the amount of magnetic flux. This structure may be designedto set the parameter τ to a suitable value for increasing the torqueoutput.

The rotor 900 of a surface magnet type shown in FIG. 53 may be used. Therotor 900 includes the rotor body 910 as an iron core and the permanentmagnets 920 with two magnetic pole pairs. The rotor body 910 has formedtherein the hole 930 through which a rotating shaft passes.

The stator winding is, as illustrated in FIG. 54 , equipped with theconductors 1041 and the seal 1042 which occupies between the conductors1041 and is made of synthetic resin. The stator winding is secured tothe stator core 1032 using adhesive, not shown. The stator core 1032 hasformed therein the protrusions 1033 located fully inside surfaces of theconductors 1041 facing the stator core 1032 in the radial direction. Theprotrusions 1033 may be implemented by convexities formed on the orderof submicrometers, such as tool marks made by a lathe machine. Theadhesive is firmly stuck to the protrusions 1033 to achieve a firm jointof the stator winding to the stator core 1032. For instance, each of theprotrusions 1033 may be shaped to have a dimension in the radialdirection which is selected in a range of 0.1 mm to 1.0 mm to conformwith a curvature of rounded conductors or a curvature of corners ofrectangular conductors.

The stator winding may be, as illustrated in FIG. 55 , equipped with theconductors 1043 and 1044 arranged in the form of two layers and the seal1045 which occupies between the conductors 1043 and 1044 and is made ofsynthetic resin. The stator winding is secured to the stator core 1034using adhesive, not shown. The stator core 1034 has the protrusions 1035formed thereon. The conductors 1043 on the first layer position arearranged closer to each other than the conductors 1044 on the secondlayer position.

In a case where there are no gaps or only small gaps between thestraight sections of the stator winding, the straight sections may beshaped to have an increased area contacting cooling liquid or air andalso to minimize the diffusion of cooling liquid from a clearancebetween the straight sections which will usually be objectionable intypical cooling systems. In this case, the straight sections each havean increased sectional area, thus resulting in a low risk of copper lossand enhancing the dissipation of heat from the straight sections.

A problem is developed that the number of stator windings arranged inparallel to each other is increased for the number of poles of a rotoror the number of phases of a stator, thereby resulting in an increase inamount of electrical current circulating between parallel arrangedconductors of the stator windings to generate reactive power. Such aproblem is alleviated by increasing the number of phases to six ortwelve.

The number of poles of the rotor may be selected to be twelve or more toomit parallel connections of six-phase stator windings which areavailable on the market for rotating electrical machines, such asalternators, for vehicles. This results in no electrical currentcirculating between the parallel arranged conductors, which facilitatesthe ease with which the rotating electrical machine is controlled orenables the stator winding to be designed to generate less heat. Therotating electrical machine equipped with six-phase windings may beremade as a three-phase rotating electrical machine by connectingtwo-phase portions of the six-phase windings parallel to each other toform three-phase windings.

Fourth Embodiment

Next, the fourth embodiment will be described below in terms ofdifferences between itself and the first embodiment with reference tothe drawings. In this embodiment, a rotating electrical machine is of aninner rotor type (i.e., an inward rotating type). FIG. 56 is alongitudinal sectional view along the rotating shaft 1101 of therotating electrical machine 1100.

The rotating electrical machine 1100 is equipped with the rotating shaft1101, two bearings 1102 and 1103, the housing 1110, the rotor 1120, andthe stator 1130 which are arranged coaxially with the rotating shaft1101.

The bearings 1102 and 1103 are disposed away from each other in theaxial direction within the housing 1110. Each of the bearings 1102 and1103 is implemented by, for example, a radial ball bearing. The bearings1102 and 1103 retain the rotating shaft 1101 to be rotatable.

The rotor 1120 includes the cylindrical rotor body 1121 and the annularmagnet unit 1122 mounted on an outer periphery of the rotor body 1121.The magnet unit 1122 is made up of a plurality of magnets whose magneticpoles are arranged alternately in the circumferential direction.

The stator 1130 is located radially outside the rotor 1120. The stator1130 includes the cylindrical stator winding 1131 and the stator core1132 arranged radially outside the stator winding 1131. The stator core1132 is of a circular ring shape and arranged radially inside thehousing 1110. The stator core 1132 is secured to the housing 1110 using,for example, adhesive. The stator core 1132 may be designed, like in thefirst embodiment, to have a slot-less structure with no teeth.

The stator winding 1131 faces the annular magnet unit 1122 through agiven air gap. The stator winding 1131 is made of a three-phase windingin the form of a full-pitch distributed winding, but however, mayalternatively be made of another type of winding. Conductors of thestator winding 1131 are, like in the first embodiment, of a flattenedshape. Each of the conductors of the stator winding 1131 is, like in thefirst embodiment, made of an aggregation of a plurality of twistedwires.

For instance, an inverter unit may be mounted radially inside the rotor1120 within the housing 1110. FIG. 56 shows a distance g1 between aradially outer periphery of the magnet unit 1122 and a radially innerperiphery of the stator core 1132 and a distance g2 between the radiallyouter periphery of the magnet unit 1122 and a radially inner peripheryof the stator winding 1131. This embodiment is capable of decreasing thewinding ratio K to reduce a magnetic resistance in a magnetic circuit.

The above embodiment has substantially the same beneficial advantages asthe first embodiment.

Modification 1 of the Fourth Embodiment

This embodiment will be described below in terms of differences betweenitself and the first embodiment. A rotating electrical machine in thisembodiment is, as illustrated in FIG. 57 , of an outer rotor structuredifferent to that in the first embodiment. FIG. 57 is a longitudinalsectional view along the rotating shaft 1201 of the rotating electricalmachine 1200.

The rotating electrical machine 1200 is equipped with the rotating shaft1201, two bearings 1202 and 1203, the housing 1210, the rotor 1220, andthe stator 1230 which are arranged coaxially with the rotating shaft1201. The bearings 1202 and 1203 are disposed away from each other inthe axial direction within the housing 1210. The bearings 1202 and 1203retain the rotating shaft 1201 to be rotatable.

The rotor 1220 includes the hollow cylindrical rotor body 1221, theannular rotor core 1222 mounted radially inside the rotor body 1221, andthe annular magnet unit 1223 arranged radially inside the rotor core1222. The magnet unit 1223 is made up of a plurality of magnets whosemagnetic poles are arranged alternately in the circumferentialdirection.

The stator 1230 is located radially outside the rotor 1220. The stator1230 includes the cylindrical stator winding 1231 and the stator core1232 arranged radially outside the stator winding 1231. The stator core1232 is of a circular ring shape. The stator core 1232 may be designed,like in the first embodiment, to have a slot-less structure with noteeth.

The stator winding 1231 faces the annular magnet unit 1223 through agiven air gap. Conductors of the stator winding 1231 are, like in thefirst embodiment, of a flattened shape. Each of the conductors of thestator winding 1231 is, like in the first embodiment, made of anaggregation of a plurality of twisted wires. FIG. 57 shows a distance g1between a radially inner periphery of the magnet unit 1223 and aradially outer periphery of the stator core 1232 and a distance g2between the radially inner periphery of the magnet unit 1223 and aradially outer periphery of the stator winding 1231.

The above embodiment has substantially the same beneficial advantages asthe first embodiment.

Modification 2 of the Fourth Embodiment

This embodiment will be described below in terms of differences betweenitself and the first embodiment. A rotating electrical machine in thisembodiment is designed not to be of a radial gap structure, but, asillustrated in FIG. 58 , of an axial gap structure. FIG. 58 is alongitudinal sectional view along the rotating shaft 1301 of therotating electrical machine 1300.

The rotating electrical machine 1300 is equipped with the rotating shaft1301, the bearing 1302, the housing 1310, the rotor 1320, and the stator1330. The bearing 1302 is disposed within the housing 1310 and made of,for example, a radial ball bearing. The bearing 1302 retains therotating shaft 1301 and the rotor 1320 to be rotatable.

The rotor 1320 includes the disc-shaped rotor body 1321, the disc-shapedmagnet unit 1322 mounted on the rotor body 1321. The magnet unit 1323 ismade up of a plurality of magnets whose magnetic poles are arrangedalternately in the circumferential direction.

The stator 1330 is arranged at a position facing the rotor 1320 in theaxial direction. The stator 1330 includes the disc-shaped stator winding1331 and the stator core 1332. The stator core 1332 is of a disc-shape.The stator core 1332 is designed to have a slot-less structure with noteeth.

The stator winding 1331 faces the disc-shaped magnet unit 1323 through agiven air gap. The stator winding 1331 is, as can be seen in FIG. 59 ,of a sector form. Conductors of the stator winding 1331 are, like in thefirst embodiment, of a flattened shape. Each of the conductors of thestator winding 1331 is, like in the first embodiment, made of anaggregation of a plurality of twisted wires. FIG. 58 shows a distance g1between a surface of the magnet unit 1322 which faces the stator winding1331 and a surface of one of axially opposed ends of the stator core1332 which faces away from the stator winding 1331 and a distance g2between the surface of the magnet unit 1322 which faces the statorwinding 1331 and a surface of the stator winding 1331 which faces themagnet unit 1322.

Typical rotating electrical machines of an axial gap structure withteeth are usually designed to have concentrated windings because of thedifficulty of a winding operation. The rotating electrical machine inthis embodiment is of the slot-less structure, thereby enabling the useof a full-pitch distributed winding which has an advantage formechanical vibration or noise.

The above embodiment has substantially the same beneficial advantages asthe first embodiment.

Modification 3 of the Fourth Embodiment

The rotating electrical machine of the axial gap structure may bedesigned, as illustrated in FIG. 60 , to be of a tandem type in whichtwo magnet units 1422 a and 1422 b are arranged to face each otherthrough the stator 1430 in the axial direction. The rotating electricalmachine 1400 includes the rotating shaft 1401, two bearings 1402 and1403, the housing 1410, the rotor 1420, and the stator 1430. The stator1430 is equipped with the first and second windings 1431 a and 1431 band the stator core 1432. The rotor 1420 includes the first and secondrotor cores 1421 a and 1421 b and the first and second magnet units 1422a and 1422 b. The structure of the rotating electrical machine 1400 inFIG. 60 is capable of increasing the torque output to be greater thanthat in the modification 3 of the fourth embodiment.

Fifth Embodiment

The stator core 52 in the first embodiment has an even curved outerperipheral surface without any irregularities and a plurality ofconductor groups 81 arranged at a given interval away from each other onthe outer peripheral surface, however, may be modified. For instance,the stator core 52 is, as illustrated in FIG. 61 , equipped with thecircular ring-shaped yoke 141 and the protrusions 142. The yoke 141 islocated on the opposite side (i.e., a lower side, as viewed in thedrawing) of the stator winding 51 to the rotor 40 in the radialdirection. Each of the protrusions 142 protrudes into an interval or gapbetween a respective two of the straight sections 83 arranged adjacenteach other in the circumferential direction. The protrusions 142 arearranged at a given interval away from each other in the circumferentialdirection radially outside the yoke 141, i.e., close to the rotor 40.Each of the conductor groups 81 of the stator winding 51 engages theprotrusions 142 in the circumferential direction, in other words, theprotrusions 142 are used as positioners to position the conductor groups81 and arrayed in the circumferential direction. The protrusions 142correspond to winding-to-winding members.

A radial thickness of each of the protrusions 142 from the yoke 141 isselected to be smaller than half a radial thickness (as indicated by H1in the drawing) of the straight sections 83 arranged adjacent the yoke141 in the radial direction. Such selection of the thickness of theprotrusions 142 causes each of the protrusions 142 not to function as atooth between the conductor groups 81 (i.e., the straight sections 83)arranged adjacent each other in the circumferential direction, so thatthere are no magnetic paths which would usually be formed by the teeth.The protrusions 142 need not necessarily to be arranged between arespective circumferentially adjacent two of all the conductor groups81. A single protrusion 142 may be disposed at least only between two ofthe conductor groups 81 which are arranged adjacent each other in thecircumferential direction. Each of the protrusions 142 may be designedto have any shape, such as a rectangular or arc-shape.

If an imaginary circle whose center is located at the axial center ofthe rotating shaft 11 and which passes through the radial centers of thestraight sections 83 placed adjacent the yoke 141 in the radialdirection is defined, each of the protrusions 142 may be shaped toprotrude only within the imaginary circle, in other words, not toprotrude radially outside the imaginary circle toward the rotor 40.

The above structure in which the protrusions 142 have the limitedthickness in the radial direction and do not function as teeth in thegaps between the straight sections 83 arranged adjacent each other inthe circumferential direction enables the adjacent straight sections 83to be disposed closer to each other as compared with a case where teethare provided in the gaps between the straight sections 83. This enablesthe conductor sectional area to be increased, thereby reducing heatgenerated upon excitation of the stator winding 51. The absence of theteeth enables magnetic saturation to be eliminated to increase theamount of electrical current delivered to the stator winding 51. It is,however, possible to alleviate the adverse effects arising from anincrease in amount of heat generated by the increase in electricalcurrent delivered to the stator winding 51. The stator winding 51, asdescribed above, has the turns 84 which are shifted in the radialdirection and equipped with the interference avoiding portions with theadjacent turns 84, thereby enabling the turns 84 to be disposed awayfrom each other in the radial direction. This enhances the heatdissipation from the turns 84. The above structure is enabled tooptimize the heat dissipating ability of the stator 50.

This embodiment described above is capable of using the protrusions 142as positioners to position and array the straight sections 83 of thestator winding 51 in the circumferential direction. This facilitates thewinding operation.

Since the thickness of the protrusions 142 is restricted in the radialdirection, the amount of interlinkage magnetic flux, as produced by themagnet unit 42, passing through portions of the straight sections 83extending outside the protrusions 142 in the radial direction isincreased. Such an increase will result in an increase in eddy current.The conductor body 82 a of each of the conductors 82 is, however, madeof an aggregation of twisted, thereby reducing the eddy current.

The protrusions 142 also cause resinous adhesive fixing the statorwinding 51 to enter between the circumferentially adjacent protrusions142, thereby enhancing joining of the stator winding 51 to the statorcore 52. The stator core 52 is made of a stack of steel plates and thushas three-dimensional irregularities in the circumferential or axialdirection, which also strengthens the securement of the stator winding51 by the stator core 52.

Modification 1 of the Fifth Embodiment

The radial thickness of the protrusions 142 may not be restricted by thedimension H1 in FIG. 25 as long as the yoke 141 of the stator core 52and the magnet unit 42 (i.e., each of the magnets 91 and 92) of therotor 40 are arranged at a given distance away from each other.Specifically, the radial thickness of the protrusions 142 may be largerthan or equal to the dimension H1 in FIG. 61 as long as the yoke 141 andthe magnet unit 42 arranged 2 mm or more away from each other. Forinstance, in a case where the radial thickness of the straight section83 is larger than 2 mm, and each of the conductor groups 81 is made upof the two conductors 82 stacked in the radial direction, each of theprotrusions 142 may be shaped to occupy a region ranging to half thethickness of the straight section 83 not contacting the yoke 141, i.e.,the thickness of the conductor 82 located farther away from the yoke141. In this case, the above beneficial advantages will be obtained byincreasing the conductive sectional area of the conductor groups 81 aslong as the radial thickness of the protrusions 142 is at least H1×3/2.

Modification 2 of the Fifth Embodiment

The stator core 52 may be designed to have the structure illustrated inFIG. 26 . FIG. 62 omits the sealing members 57, but the sealing members57 may be used. FIG. 26 illustrates the magnet unit 42 and the statorcore 52 as being arranged linearly for the sake of simplicity.

In the structure of FIG. 62 , the stator 50 has the protrusions 142 aswinding-to-winding members each of which is arranged between arespective two of the conductors 82 (i.e., the straight sections 83)located adjacent each other in the circumferential direction. If a widthof the protrusions 142 energized by excitation of the stator winding 51in the circumferential direction within a portion of the magnet unit 42equivalent to one of magnetic poles thereof is defined as Wt, thesaturation magnetic flux density of the protrusions 412 is defined asBs, a width of the magnet unit 42 equivalent to one of the magneticpoles of the magnet unit 42 in the circumferential direction of themagnet unit 42 is defined as Wm, and the remanent flux density in themagnet unit 42 is defined as Br, the protrusions 142 are made of amagnetic material meeting a relation ofWt×Bs≤Wm×Br  (1)

Specifically, the three-phase windings of the stator winding 51 in thisembodiment are made in the form of distributed windings. In the statorwinding 51, the number of the protrusions 142 for each pole of themagnet unit 42, that is, the number of the gaps 56 each between theadjacent conductor groups 81 is given by 3×m where m is the number ofpairs of the conductors 82. In this case, when the three-phase windingsof the stator winding 51 are excited in a given sequence, theprotrusions 142 for two phases within each pole are magneticallyexcited. The width Wt of the protrusions 142 excited upon excitation ofthe stator winding 51 within a range of each pole of the magnet unit 42is, therefore, given by 2×A×m where A is the width of each of theprotrusions 142 (i.e., the gap 56) in the circumferential direction. Thewidth Wt is determined in this way. The protrusions 142 of the statorcore 52 are made from magnetic material satisfying the above equation(1). The width Wt is also equivalent to a dimension of a portion of thestator 50 where a relative magnetic permeability is higher than 1 withinone magnetic pole in the circumferential direction.

In the case where the stator winding 51 is made in the form of theconcentrated winding, the number of the protrusions 142 for one polepair (i.e., two magnetic poles) of the magnet unit 42, in other words,the number of the gaps 56 between the conductor groups 81 for one polepair is given by 3×m. When the three-phase windings of the statorwinding 51 are excited in a given sequence, the protrusions 142 for onephase within one pole are magnetically energized. The circumferentialwidth Wt of the protrusions 142 which are magnetically excited uponexcitation of the stator winding in a range of each pole of the magnetunit 42 is, therefore, given by Wt=A×m. The width Wt is determined inthis way. The protrusions 142 are made of magnetic material meeting theabove equation (1).

Usually, a neodymium magnet, a samarium-cobalt magnet, or a ferritemagnet whose value of BH is higher than or equal to 20[MGOe(kJ/m{circumflex over ( )}3)] has Bd=1.0 T or more. Iron has Br=2.0 T ormore. The protrusions 142 of the stator core 52 may, therefore, be madeof magnetic material meeting a relation of Wt<1/2×Wm for realizing ahigh-power motor.

Modification 3 of the Fifth Embodiment

The above embodiment has the sealing members 57 which cover the statorwinding 51 and occupy a region including all of the conductor groups 81radially outside the stator core 52, in other words, lie in a regionwhere the thickness of the sealing members 57 is larger than that of theconductor groups 81 in the radial direction. This layout of the sealingmembers 57 may be changed. For instance, the sealing members 57 may be,as illustrated in FIG. 63 , designed so that the conductors 82 protrudepartially outside the sealing members 57. Specifically, the sealingmembers 57 are arranged so that portions of the conductors 82 that areradially outermost portions of the conductor groups 81 are exposedoutside the sealing members 57 toward the stator 50. In this case, thethickness of the sealing members 57 in the radial direction may beidentical with or smaller than that of the conductor groups 81.

The sealing members 57 are shaped to have the conductors 82 partiallyexposed outside the sealing members 57, so that the exposed portions ofthe conductors 82 are cooled by air. This enhances the dissipation ofheat from the conductors 82.

The structure in FIG. 63 is not equipped with the protrusions 142, butmay alternatively have them.

Modification 4 of the Fifth Embodiment

The stator 50 may be, as illustrated in FIG. 64 , designed not to havethe sealing members 57 covering the conductor groups 81, i.e., thestator winding 51. In this case, a gap is created between the adjacentconductor groups 81 arranged in the circumferential direction withoutany tooth.

The structure in FIG. 64 is not equipped with the protrusions 142, butmay alternatively have them.

Sixth Embodiment

In this embodiment shown in FIG. 65 , the distance DM between a radiallyinner surface of the magnet unit 42 (i.e., the first and second magnets91 and 92) and the axial center of the rotor 40 in the radial directionis selected to be 50 mm or more.

If a distance between a radially outer surface of the magnet unit 42 anda radially inner surface of the stator winding 51 in the radialdirection is defined as LS, and a thickness of the magnet unit 42 in theradial direction is defined as LM, LM/LS is selected to be 0.6 or moreand 1.0 or less.

If a first distance and a second distance are defined as MA and MB,respectively, MB/MA is selected to be 0.7 or more and 1.0 or less. Thefirst distance MA is a distance between the axial center of the rotor 40and the radially outer surface of the magnet unit 42. In other words,the first distance MA is a maximum value from the axial center of therotor 40 in the radial direction in a magnetic circuit of the stator 50and the rotor 40. The second distance MB is a distance between the axialcenter of the rotor 40 and the radially inner surface of the stator core52. In other words, the second distance MB is a minimum value from theaxial center of the rotor 40 in the radial direction in the magneticcircuit.

If a length of a portion of the magnetic unit 42 equivalent to onemagnetic pole in the circumferential direction is, as illustrated inFIG. 66 , defined as Cs, 2×DM/Cs is selected to be 3.5 or more and 12 orless.

The thickness G1 of the stator core 52 in the radial direction is, asillustrated in FIG. 66 , selected to be smaller than the thickness G2 ofthe magnet unit 42 in the radial direction and greater than thethickness G3 of the stator winding 51 in the radial direction.

The above embodiment offers the following beneficial advantages.

The outer rotor structure of the rotating electrical machine 10 isdesigned to have LM/LS selected to be 0.6 or more and 1.0 or less. Thegreater the LM/LS, the grater the thickness of the magnet unit 42 in theradial direction, thereby resulting in an increase in magnetomotiveforce produced by the magnet unit 42. This results in an increase inmagnetic flux density in the stator winding 51 to enhance the torqueoutput of the rotating electrical machine 100. The greater LM/LS, thesmaller the air gap between the magnet unit 42 and the stator winding51, thereby resulting in a decrease in magnetic resistance in themagnetic circuit to increase the torque output. By selecting LM/LS to be0.6 or more, a structure is established to be suitable for increasingthe torque output.

MB/MA is selected to be 0.7 or more and 1.0 or less. The fact that MB/MAis great means that the magnetic circuit has a thickness decrease in theradial direction. The decreased thickness of the magnetic circuit in theradial direction means the magnetic path is shortened to decrease themagnetic resistance. The structure suitable for decreasing the magneticresistance is, therefore, established by selecting MB/MA to be 0.7 ormore. This enhance the torque output.

The outer rotor structure in which MB/MA is great means the casing 64has formed therein a storage space for storage of the electricalcomponents 62.

The thickness G1 of the stator core 52 in the radial direction isselected to be smaller than the thickness G2 of the magnet unit 42 inthe radial direction and greater than the thickness G3 of the statorwinding 51. This enables the stator core 52 to receive magnetic fluxproduced by the magnet unit 42 without any magnetic saturation and alsoeliminates a risk of leakage of magnetic flux from the stator 50.

The size of the stator winding 51 may be decreased relatively by meetinga relation of G3<G1<G2, which achieves LM/LS that is 0.6 or more.

Modification 1 of the Sixth Embodiment

The structure in the sixth embodiment may be used in the secondembodiment. The second distance MB is selected to be the same value asin the fourth embodiment, while the first distance MA is set to adistance or an interval between a portion of the rotor body 41 which islocated away from the radially outer surface of the magnet unit 42 by adistance df outward in the radial direction and the axial center of therotor 40 in the radial direction. The reason why the first distance MAis defined as being away from the magnet unit 42 by the distance df isthat in the Halbach array, the magnetic flux produced by the magnet unit42 partially leaks toward the rotor body 41. The distance df is, as canbe seen in FIG. 67 , from the radially outer surface of the magnet unit42 by half a distance between magnetic poles of the magnet unit 42 inthe circumferential direction. FIG. 67 illustrates the magnet retainer43 of the rotor body 41 and the magnet unit 42 as being developedlinearly. The lower side in FIG. 67 is a side of the rotor 40. The upperside in FIG. 67 is a side of the stator 50. Arrows in FIG. 67 representmagnetic poles defined by the sum of magnetic fluxes produced by thefirst and second magnets 131 and 132.

Modification 2 of the Sixth Embodiment

The magnet unit 42 may be, as illustrated in FIG. 68 , magnetized in theradial direction. The magnet unit 42 includes the first magnets 137whose magnetization direction is oriented inwardly in the radialdirection and the second magnets 138 whose magnetization direction isoriented outwardly in the radial direction. The first and seconddistances MA and MB are the same as in the fourth embodiment.

Modification 3 of the Sixth Embodiment

The modification 3 will be described below in terms of differencesbetween itself and the sixth embodiment with reference to the drawings.The rotating electrical machine in this embodiment is of the inner rotorstructure (i.e., the inwardly rotating structure). FIG. 68 is alongitudinal sectional view along the rotating shaft 1501 of therotating electrical machine 1500.

The rotating electrical machine 1500 is equipped with the rotating shaft1501, two bearings 1502 and 1503, the housing 1510, the rotor 1520, andthe stator 1530 which are arranged coaxially with the rotating shaft1501.

The bearings 1502 and 1503 are disposed away from each other in theaxial direction within the housing 1510. Each of the bearings 1502 and1503 is implemented by, for example, a radial ball bearing. The bearings1502 and 1503 retain the rotating shaft 1501 and the rotor 1520 to berotatable.

The rotor 1520 includes the cylindrical rotor body 1521 and the annularmagnet unit 1522 mounted radially outside the rotor body 1521. Themagnet unit 1522 is made up of a plurality of magnets whose magneticpoles are arranged alternately in the circumferential direction. In thisembodiment, the magnet unit 1522 has a structure similar to the polaranisotropic structure in the first embodiment.

The stator 1530 is located radially outside the rotor 1520. The stator1530 includes the cylindrical stator winding 1531 and the stator core1532 arranged radially outside the stator winding 1531. The stator core1532 is of a circular ring shape and disposed radially inside thehousing 1510. The stator core 1532 is secured to the housing 1510 using,for example, adhesive. The stator core 1532 may be designed, like in thefirst embodiment, to have a slot-less structure with no teeth.

The stator winding 1531 faces the annular magnet unit 1522 through agiven air gap. The stator winding 1531 is made of a three-phase windingin the form of a full-pitch distributed winding, but however, mayalternatively be made of another type of winding. Conductors of thestator winding 331 are, like in the first embodiment, of a flattenedshape. Each of the conductors of the stator winding 1531 is, like in thefirst embodiment, made of an aggregation of a plurality of twistedwires.

For instance, the housing 1510 has inverter units disposed radiallyinside the rotor 1520.

The rotating electrical machine 1500 in this embodiment is of the innerrotor structure. The second distance MB is, therefore, a distancebetween the axial center of the rotor 1520 and a radially inner surfaceof the stator core 1532 in the radial direction. The rotating electricalmachine 1500 uses polar anisotropic permanent magnets, so that the firstdistance MA is a distance between the axial center of the rotor 1520 anda radially outer surface of the stator core 1532 in the radialdirection.

Modification 4 of the Sixth Embodiment

The magnet unit 1523 may alternatively be, as illustrated in FIG. 70 ,designed to include permanent magnets arranged in the Halbach array usedin the second embodiment or magnets used in the modifications of thesecond embodiment. In this case, the second distance MB is the same asin the fourth embodiment. The first distance MA is selected to be adistance or an interval between a place located radially inwardly awayfrom the radially inner surface of the stator core 1532 by df/2 and theaxial center of the rotor 1520 in the radial direction.

Modification 5 of the Sixth Embodiment

The modification 5 will be described below in terms of differencesbetween itself and the first embodiment. A rotating electrical machinein this embodiment is, as illustrated in FIG. 71 , of the outer rotorstructure different to that in the first embodiment. FIG. 71 is alongitudinal sectional view along the rotating shaft 1601 of therotating electrical machine 1600.

The rotating electrical machine 1600 is equipped with the rotating shaft1601, two bearings 1602 and 1603, the housing 1610, the rotor 1620, andthe stator 1630 which are arranged coaxially with the rotating shaft1601. The bearings 1602 and 1603 are disposed away from each other inthe axial direction within the housing 1610. The bearings 1602 and 1603retain the rotating shaft 1601 and the rotor 1620 to be rotatable.

The rotor 1620 includes the hollow cylindrical rotor body 1621, theannular rotor core 1622 mounted radially inside the rotor body 1621, andthe annular magnet unit 1623 arranged radially inside the rotor core1622. The magnet unit 1623 is made up of a plurality of magnets whosemagnetic poles are arranged alternately in the circumferentialdirection.

The stator 1630 is located radially inside the rotor 1620. The stator1630 includes the cylindrical stator winding 1631 and the stator core1632 arranged radially inside the stator winding 1631. The stator core1632 is designed, like in the first embodiment, to have a slot-lessstructure with no teeth.

The stator winding 1631 faces the annular magnet unit 1623 through agiven air gap. Conductors of the stator winding 1231 are, like in thefirst embodiment, of a flattened shape. Each of the conductors of thestator winding 1631 is, like in the first embodiment, made of anaggregation of a plurality of twisted wires.

The stator core 1632 in this embodiment is different in shape from thestator core 52 in the first embodiment. The first embodiment uses theouter peripheral surface of stator core 52 as the basis for determiningthe second distance MB, but however, it is infeasible in thisembodiment. The basis for the second distance MB in the stator core 1632may, therefore, be determined using simulations.

Other Embodiments

The above embodiments may be modified in the following ways.

The stator 50 may be designed not to have the stator core 52.Specifically, the stator 50 may be made of the stator winding 51 shownin FIG. 12 . The stator winding 51 of the stator 50 may be covered witha sealing member. The stator 50 may alternatively be designed to have anannular winding retainer made from non-magnetic material, such assynthetic resin, instead of the stator core 52 made from soft magneticmaterial.

In the above embodiments, the rotating shaft 11 is designed to extendoutside the ends of length of the rotating electrical machine 10, buthowever, may alternatively be designed to protrude outside only one ofthe ends of the rotating electrical machine 10. In this case, it isadvisable that a portion of the rotating shaft 11 which is retained bythe bearing unit 20 in the cantilever form be located on one of the endsof the rotating electrical machine, and that the rotating shaft 11 bearranged to extend outside such an end of the rotating electricalmachine. This structure has the rotating shaft 11 not protruding insidethe inverter unit 60, thus enabling a wide inner space of the inverterunit 60, i.e., the cylinder 71 to be used.

Bearings may be mounted on both axial ends of the rotor 40 for retainingthe rotating shaft 11 to be rotatable. For example, the structure ofFIG. 1 may have bearings mounted on or opposite sides of the inverterunit 60 in the axial direction.

The conductor body 82 a of each of the conductors 82 of the statorwinding 51 in the above embodiments is made of a collection of the wires86, however, may alternatively be formed using a square conductor havinga rectangular cross section. The conductor 82 may alternatively be madeusing a circular or rounded conductor having a circular cross section oran oval cross section.

The stator winding 51 in the above embodiments has the straight sections83 which are arranged on the same pitch circle defined about the centerof the rotating shaft 11 and joined together by the turns 84 equippedwith the interference avoiding portions. Such a structure may bemodified. For instance, the stator winding 51 may alternatively bedesigned to have the straight sections 83 which are located at differentpitch circles defined about the center of the rotating shaft 11 andjoined together by the turns 84. In either case, each of the turns 84needs to have a portion extending in the radial direction to form aninterference avoiding portion which avoids physical interference withanother turn 84.

The interference between the radially overlapping conductors 82 of eachof the conductor groups 82 of the stator winding 51 may alternatively beavoided by orienting portions of the turns 84 located at the n^(th)layer position and the (n+1)^(th) layer position in opposite directionsor placing portions of the turns 84 located at the n^(th) layer positionand the (n+1)^(th) layer position at different locations.

The stator winding 51 may be designed to have the conductors 82 each ofwhich is made of a single straight section 83. Each of the conductors 82may alternatively be made of three or more straight sections 83 (e.g.,three, four, five, or six straight sections 83) stacked in a multi-layerform in the radial direction of the stator winding 51.

The structure of the above embodiments has the inverter unit 60 arrangedradially inside the stator 50, but however, may alternatively bedesigned not to have the inverter 60 disposed inside the stator 50. Thisenables the stator 50 to have a radial inner void space in which partsother than the inverter unit 60 may be mounted.

For instance, a voltage converter, such as a transducer, may be disposedin the inner void space of the stator 50. The voltage converter may beengineered to excite the stator winding 51 at a high frequency toperform voltage conversion without any copper loss. This, however,creates an electromagnetic chair or seat. The stator 50, the rotor 40,and the housing 30, however, work to prevent it from leaking to theoutside.

For instance, a speed reduction mechanism (i.e., a power transmissionmechanism), such as a set of gears, may be disposed in the inner voidspace of the stator 50. The power transmission mechanism sometimesgenerates frictional heat more than 100° C., however, it may be arrangedin the first region X1 (i.e., an inside region) which has a high thermalcapacity, so that it is sufficiently cooled by the coolant path 74. Thedissipation of the heat may also be enhanced by additionally using oilcooling.

The rotating electrical machine 10 may be designed not to have thehousing 30. In this case, the rotor 40 or the stator 50 may be retainedby a wheel or another part of a vehicle.

In the above embodiments, the rotor 40 is implemented by a surfacepermanent magnet (SPM) rotor, but however, may alternatively made of aninterior permanent magnet (IPM) rotor.

In the above embodiments, the rotating shaft 11 is retained by the twobearings 21 and 22, but however, may be held by three or more bearings.

The type of the bearings 21 and 22 used in the above embodiments may bechanged as needed. The bearings 21 and 22 may be each implemented by notonly a radial ball bearing, but also a rolling bearing or a plainbearing.

The rotor body 41 in the above embodiments has an opening facing awayfrom the bearings 21 and 22 in the axial direction, but mayalternatively be designed to have a closed end.

The intermediate portion 45 or the housing 30 may have an air vent holeextending therethrough in the axial direction in order to create a flowof air to facilitate dissipation of heat.

The conductor body 82 a of each of the conductors 82 of the statorwinding 51 may be made of a conductive material, such as copper,aluminum, or copper alloy.

The wire referred to in the first embodiment may alternatively be madeof copper or aluminum.

The stator 50 in the above embodiments is of the slot-less structure,but however, may be engineered to have slots.

The rotating electrical machine will additionally be described below.

If a diameter of an imaginary circle defined to pass through the radialcenter of an air gap between the rotor 40 and the stator 50 is definedas D, and the number of poles in the rotating electrical machine isdefined as P, the inner diameter of the stator 50 is selected to meet acondition where D/P is less than 12.2. FIG. 72 represents space createdinside conductors wound in the stator 50, i.e., the diameter d×Z (1 orless) where the conductors wound in the stator 50 of the rotatingelectrical machine are engineered to lie in a range of 20[A/mm{circumflex over ( )}2] to 40[A/mm{circumflex over ( )}2] which isusually set as a maximum electrical current in typical rotatingelectrical machines. By selecting D/P to be 12.2 or less, the wide innerspace is provided with the reliability of conventional technology beingkept as it is.

While this disclosure has been discussed in terms of the preferredembodiments in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, thisdisclosure should be understood to include all possible embodiments andmodifications to the shown embodiments which can be embodied withoutdeparting from the principle of this disclosure as set forth in theappended claims.

What is claimed is:
 1. A rotating electrical machine comprising: a rotorwhich is equipped with a magnet unit which generates magnetic flux andretained to be rotatable; and a stator which is equipped with a statorwinding made up of a plurality of phase windings, the stator beingarranged coaxially with the rotor and facing the rotor, wherein themagnet unit includes first magnets whose magnetization direction isoriented in a radial direction of the rotor and second magnets whosemagnetization direction is oriented in a circumferential direction ofthe rotor, the first magnets are arranged at a given interval away fromeach other in the circumferential direction, and each of the secondmagnets is disposed in the circumferentially adjacent first magnets, themagnet unit has end surfaces of the first magnets which face away fromthe stator and end surfaces of the second magnets which face away fromthe rotor, at least the end surfaces of the first magnets or the endsurfaces of the second magnets define recesses hollowed toward thestator in the radial direction, magnetic members are disposed in therecesses in a surface of the rotor which faces away from the stator, athickness of either of the first magnets or the second magnets in theradial direction is set smaller than that of the other of the firstmagnets and the second magnets to define the recesses, and the magneticmembers are arranged away from the stator in the first magnets or thesecond magnets, whichever are smaller in thickness.
 2. The rotatingelectrical machine as set forth in claim 1, wherein ones of the firstmagnets have magnetization directions oriented toward the stator, themagnetic members being disposed in the ones of the first magnets awayfrom the stator.
 3. The rotating electrical machine as set forth inclaim 1, wherein the rotor is equipped with a magnet retainer which ismade from soft magnetic material and retains the magnetic memberstogether with the magnet unit, and wherein the magnet retainer isdisposed on a portion of the magnet unit which faces away from thestator, and the magnet retainer extends over the first magnets and thesecond magnets which are disposed adjacent each other in thecircumferential direction.
 4. The rotating electrical machine as setforth in claim 1, wherein the second magnets have a length in thecircumferential direction which lies in a range of 52<α<80 where α is anelectrical angle [degE].
 5. The rotating electrical machine as set forthin claim 1, wherein the rotor is of an outer rotor structure in whichthe rotor is arranged radially outside the stator.
 6. The rotatingelectrical machine as set forth in claim 1, wherein the rotor isequipped with a magnet retainer which retains said magnetic memberstogether with the magnet unit, and wherein the magnetic members areequipped with engaging portions which are arranged in thecircumferential direction and engage the magnet retainer.
 7. Therotating electrical machine as set forth in claim 1, wherein said firstmagnets include a first A magnet whose magnetization direction isoriented outwardly in the radial direction and a first B magnet whosemagnetization direction is oriented inwardly in the radial direction,wherein the second magnets include a second A magnet whose magnetizationdirection is oriented in a first one of opposite circumferentialdirection and a second B magnet whose magnetization direction isoriented in a second one of the opposite circumferential direction, andwherein the magnet unit has the first A magnet, the second A magnet, thefirst B magnet, and the second B magnet arranged in this order in thecircumferential direction.
 8. A rotating electrical machine comprising:a rotor which is equipped with a magnet unit which generates magneticflux and retained to be rotatable; and a stator which is equipped with astator winding made up of a plurality of phase windings, the statorbeing arranged coaxially with the rotor and facing the rotor, whereinthe magnet unit includes first magnets whose magnetization direction isoriented in a radial direction of the rotor and second magnets whosemagnetization direction is oriented in a circumferential direction ofthe rotor, the first magnets are arranged at a given interval away fromeach other in the circumferential direction, and each of the secondmagnets is disposed in the circumferentially adjacent first magnets, themagnet unit has end surfaces of the first magnets which face away fromthe stator and end surfaces of the second magnets which face away fromthe rotor, at least the end surfaces of the first magnets or the endsurfaces of the second magnets define recesses hollowed toward thestator in the radial direction, magnetic members are disposed in therecesses in a surface of the rotor which faces away from the stator, thefirst magnets have a thickness in the radial direction which is selectedto be smaller than that of the second magnets to define the recesses,the magnetic members are disposed in portions of the first magnets whichare located away from the stator, and the sum of the thickness of eachof the first magnets and a thickness of a corresponding one of themagnetic members in the radial direction is equal to the thickness ofeach of the second magnets in the radial direction.
 9. A rotatingelectrical machine comprising: a rotor which is equipped with a magnetunit which generates magnetic flux and retained to be rotatable; and astator which is equipped with a stator winding made up of a plurality ofphase windings, the stator being arranged coaxially with the rotor andfacing the rotor, wherein the magnet unit includes first magnets whosemagnetization direction is oriented in a radial direction of the rotorand second magnets whose magnetization direction is oriented in acircumferential direction of the rotor, the first magnets are arrangedat a given interval away from each other in the circumferentialdirection, and each of the second magnets is disposed in thecircumferentially adjacent first magnets, the magnet unit has endsurfaces of the first magnets which face away from the stator and endsurfaces of the second magnets which face away from the rotor, at leastthe end surfaces of the first magnets or the end surfaces of the secondmagnets define recesses hollowed toward the stator in the radialdirection, magnetic members are disposed in the recesses in a surface ofthe rotor which faces away from the stator, the second magnets have athickness in the radial direction which is selected to be smaller thanthat of the first magnets to define the recesses, the magnetic membersare disposed in portions of the second magnets which are located awayfrom the stator, and the sum of the thickness of each of the secondmagnets and a thickness of a corresponding one of the magnetic membersin the radial direction is equal to the thickness of each of the firstmagnets in the radial direction.